OBJECTIVE: To develop a reversed phase HPLC method for the quantitative determination of the ergot fermentation product α-ergocryptine and to determine the peak value of α-ergocryptine yielded during the fermentation. METHODS: A YWG-C₁₈column (250 mm×4.6 mm ID,particle size,10 μm) was used;the mobile phase was MeOHphosphate buffer (pH7.0)EtOAc (75∶25∶1) with a flow rate of 1.0 ml·min^-1and detected at 312 nm.A regression equation was set up,the precision of the method and the recovery rates were measured. RESULTS: Regression equation was A=19058.54M+1352.66,r=0.9997,over the range of 0.6375～6.4375 μg;the RSD for the intra day and inter day was 1.15%,0.44%,respectively;the mean recoveries were 108.48%,105.15% and 109.53% versus the added authentic sample at the concentrations of 122,244 and 488 μg·ml^-1,respectively.The peak value appeared between day 15 to day 17 under the given condition. CONCLUSION: The method is sensitive and reproducible for the quantitative determination of the ergot fermentation product α-ergocryptine.