Abstract：Objective：To investigate the possible mechanism of Kunxian Capsules in treating rats with traumatic myositis ossificans. Methods： Seventy-eight SD rats were selected and divided into the blank group (6 rats)， the sham operation group (24 rats)， the control group (24 rats) and the medicine group (24 rats) according to the random number table method. Rats in the blank group were directly executed and blood was collected；rats in the sham operation group were sutured after their ankle epidermis being cut； rats in the control group and the medicine group were established models with traumatic myositis ossificans；rats in the control group were given placebo by gavage；rats in the sham operation group and the medicine group were given decoction of Kunxian Capsules by gavage. Six rats were respectively executed by neck dissection on day 14，day 28，day 42 and day 56 after operation. The swelling thickness of ankle joint was measured before and after modeling and the joint swelling rates were counted. The levels of serum inflammatory factors [tumor necrosis factor-α (TNF-α)，interleukin-6 (IL-6)，C-reactive protein (CRP)]， bone morphogenetic protein-4 (BMP4) and Smad5 were detected by Enzyme-Linked Immunosorbent Assay (ELISA)， and the expressions of BMP4 and Smad5 in achilles tendon tissue was detected by immunohistochemistry. Results：The ankle swelling rates in the control group and the medicine group on day 14，day 28，day 42 and day 56 after operation were higher than those in the sham operation group (P＜0.01). The ankle swelling rates in the medicine group on day 42 and day 56 after operation were lower than those in the control group (P＜0.01). The serum TNF- α levels in the control group and the medicine group were higher than those in the sham operation group on day 14，day 28，day 42 and day 56 after operation (P＜0.01)； the serum TNF- α levels in the medicine group were lower than those in the control group on day 28，day 42 and day 56 after operation (P＜0.01). The serum IL-6 levels in the control group were higher than those in the sham operation group on day 14， day 28， day 42 and day 56 after operation (P＜0.01)； the serum IL-6 levels in the medicine group were higher than those in the sham operation group on day 14， day 28 and day 42 after operation (P＜0.01). The serum IL-6 levels in the medicine group were lower than those in the control group on day 14， day 28， day 42 and day 56 after operation (P＜0.01). The serum CRP levels in the control group and the medicine group were higher than those in the sham operation group on day 14， day 28， day 42 and day 56 after operation (P＜0.01)； the serum CRP levels in the medicine group were lower than those in the control group on day 42 and day 56 after operation (P＜0.01). The serum BMP4 levels in the control group were higher than those in the sham operation group on day 14，day 28，day 42 and day 56 after operation (P＜0.01)；the serum BMP4 levels in the medicine group were higher than those in the sham operation group on day 14，day 28 and day 42 after operation (P＜0.01)； the serum BMP4 levels in the medicine group were lower than those in the control group on day 28，day 42 and day 56 after operation (P＜0.01). The serum Smad5 levels in the control group were higher than those in the sham operation group on day 14， day 28， day 42 and day 56 after operation (P＜0.01)； the serum Smad5 levels in the medicine group were higher than those in the sham operation group on day 14， day 28 and day 42 after operation (P＜0.01). The serum Smad5 level in the medicine group was lower than that in the control group on day 56 after operation (P＜0.01). The average optical density of BMP4 in the control group on day 14， day 28， day 42 and day 56 after operation was higher than that in the sham operation group (P＜0.01)， and the average optical density of BMP4 in the medicine group on day 14， day 28 and day 42 after operation was higher than that in the sham operation group (P＜0.01)； the average optical density of BMP4 in the medicine group on day 28， day 42 and day 56 after operation was lower than that in the control group (P＜0.01). The average optical density of Smad5 in the control group on day 14，day 28，day 42 and day 56 after operation was higher than that in the sham operation group (P＜0.01)，and the average optical density of Smad5 in the medicine group on day 14，day 28 and day 42 after operation was higher than that in the sham operation group (P＜0.01). The average optical density of Smad5 in the medicine group on day 28， day 42 and day 56 after operation was lower than that in the control group (P＜0.01). Conclusion： The therapeutic effect of Kunxian Capsules on traumatic myositis ossificans may be related to the regulation of BMP4/Smad5 signaling pathway and the inhibition of downstream inflammatory factors.