ObjectiveTo discuss the law of clinical prescriptions for endogenous diseases in Zhoushan Medical Case Records.MethodsOne hundred and fifty medical cases of endogenous diseases in Zhoushan Medical Case Records were selected，and recordings of prescriptions were extracted and sorted out to establish a database via office 2010.IBM SPSS Modeller 14.1 was employed for the analysis of dosage，nature-flavor and channel-tropism，medication category，and association rules so as to conduct data mining.ResultsThe analysis of core medications suggested that commonly-used medications were given priority to reinforcing medicine，heat-clearing medicine and phlegm-expelling medicine.Light-floating medications featured in the administration.Based on association rules，the analysis found 8 groups of commonly-used compatible medications of two relevant herbs，9 groups of compatible medications of three herbs and 5 groups compatible medications of four herbs.ConclusionTang's treatment of endogenous diseases generally starts from lung and spleen to strengthen spleen-yang，tonify spleen-stomach and regulate lung-qi.The combined methods of reinforcing deficiency，clearing heat and dispelling phlegm are applied in the treatment as well to reinforce vital qi and smooth liver-qi and regulate qi movement，so that yin and yang in human body can ascend and descend in order.Moreover，qi can flow smoothly and restriction and generation of five phases can coordinate well，so that a good environment is established for human diseases to recovery.Meridian and viscera，as well as the movement of qi， blood and body fluid can function as normal，so endogenous diseases can be easy to cure.