Objective To evaluate the mechanism of Yang Gan Li Dan Granule-a Chinese herbal medicine in the prevention and treatment of gallstone disease Methods In a prospective controlled clinical trial from 1999 to 2003,36 patients(12 males and 24 females with a mean age of 59)with choledocholithiasis after choledochotomy were divided into the treatment group(n=24)and the control(n=12).Yang Gan Li Dan Granule was given to the treatment group.Bile and blood samples were collected on the 1 st,7th,14ath days after operation to determine biochemical indices,including total bilirubin(TB),cholesterol(Chol),total bile salt(TBS),phospholipids(PL),the colligation titer of gallstone formation tendency of bile(Z).All the data were analyzed statistically using SPSS10.0.Results Compared to the control group on the 14 th postoperative day Chol,TBS,PL of bile tended to be prone to the lysis of stone,the Z of the treatment group was lower than that of the control(P￡005). Conclusion Yang Gan Li Dan Granule can reduce lithogenic factors in the bile and abate slower the tendency of gallstone formation.It can be an available treatment of choice in preventing postoperative recurrence of choledocholithiasis.