OBJECTIVE：To investigate t he effects of different compatibility ratio of Gardenia jasminoides to fermented soybean on the content of genistein and total flavonoids ，and to investigate the compatibility regularity of Zhizichi decoction. METHODS：The decoction method was used to prepare the mixed decoction with different compatibility ratio of G. jasminoides to fermented soybean （2∶1，1∶1，1∶2，1∶4，m/m，the same hereinafter ）. UPLC-MS/MS method was used to determine the content of genistein in Zhizichi decoction with different compatibility ratio and corresponding fermented soybean single decoction. UV method was used to determine the content of total flavonoids in Zhizichi decoction with different compatibility ratio and corresponding gardenia single decoction and fermented soybean single decoction. RESULTS ：The established method had good linearity ， precision，repeatability，stability and accuracy. Compared with single decoction ，the content of genistein in the mixed decoction with different compatibility ratio of G. jasminoides to fermented soybean （2∶1，1∶1，1∶2，1∶4）was decreased to different extents ， while the content of total flavonoids was increased to different extents. With the increase of fermented soybean ，the content of genistein in the decoction increased at first and then decreased. When the compatibility ratios of G. jasminoides to fermented soybean were 1 ∶ 1 and 1 ∶ 2，the content of genistein in the decoction was the highest （all 0.071 μg/mL）. With the increase of fermented soybean ，the content of total flavonoids in the decoction did not change regularly ；when the ratio of G. jasminoides to fermented soybean was 1 ∶ 1，the content of total flavonoids in the decoction was the highest （1.861 μg/mL）. CONCLUSIONS ： When the compatibility ratio of G. jasminoides to fermented soybean was 1 ∶ 1，the content of flavonoids in the decoction is the highest.