Objective：To discuss the syndrome and law of drug using of Chinese medicine for polycystic ovary syndrome via data mining.Methods： The statistics of prescriptions mainly came from CNKI Database(1956-2016)， CHKD Patent Full-text Database(2010-2016)and the book series of hundreds of Chinese medicine clinicians in centuries.Sorted out the 352 prescriptions after screening by syndrome differentiation so as to establish the database，and analyzed their syndrome typing and law of drug using by using association rules and entropy clustering algorithm.Results：352 prescriptions involved 28 types of syndrome and 109 types of syndrome combination；among 28 types of sub-syndrome，there were 11 types of deficiency syndrome and 8 types of depression syndrome；there were 13 types of core sub-syndrome，8 types of deficiency syndrome and 4 types of depression syndrome；7 types of sub-syndrome with comparatively high frequency were phlegm depression＞blood stasis＞kidney deficiency＞dampness depression＞liver depression＞blood deficiency＞spleen deficiency；the combinations with the frequency of more than 8 times in the mode of sub-syndrome combination were phlegm depression-dampness depression，kidney deficiency-phlegm depression，phlegm depression-blood stasis，kidney deficiency-blood deficiency，kidney deficiency-dampness depression，kidney deficiency-blood stasis， liver depression-kidney deficiency，liver depression-phlegm depression；among the syndrome combination，the type of kidney deficiency and blood stasis and the type of liver depression and kidney deficiency are of the highest quantity，and then followed by the phlegm-dampness type，the type of phlegm-blood stasis and the type of qi depression and blood stasis.Among 350 Chinese herbs under selection，their properties and tastes were mainly warmth and sweetness，and the channel tropism was mainly into the liver channel；top 10 Chinese herbs with the highest using frequency were angelica sinensis，cuscuta chinensis lam，Cyperus rotundus L.，Poria cocos，prepared radix rehmanniae，radices paeoniae alba，rhizome of chuanxiong，salvia，wolfberry fruit and licorice；top 7 Chinese herbs with the highest using frequency for the type of kidney deficiency and blood stasis were angelica sinensis，cuscuta chinensis lam，salvia，red pony root，rhizoma cyperi，Chinese yam and cornus officinalis；top 7 Chinese herbs with the highest using frequency for the type of liver depression and kidney deficiency were angelica sinensis，bupleurum，cuscuta chinensis lam，rhizoma cyperi，Poria cocos，salvia and radices paeoniae alba；top 7 Chinese herbs with the highest using frequency for the phlegm-dampness type were Poria cocos，Pinellia ternate， tangerine peel， angelica sinensis， rhizoma cyperi， rhizome of chuanxiong and atractylodes rhizome.Conclusion： As analytical results shows， the functional disorder of kidney， spleen and liver is the main pathogenesis；dampness，phlegm and stasis are the main pathogenic factors；deficiency and depression are the manifestations in the nature of disease； yin-invigoration and depression-relieving are the fundamental methods for PCOS， while kidneytonification and spleen-fortification，liver-soothing and depression-relieving，qi-regulating and phlegm-resolving are the main thinking in treating PCOS.