Abstract: Tomato was used as raw material for natural fermentation,and the inhibition effect of fermentation broth on alpha-amylase was studied. The effects of different dilution times,time,pH and temperature of fermentation broth on the inhibition of alpha-amylase were analyzed by 3,5-dinitrosalicylic acid colorimetry;Lineweaver-Burk double reciprocal method was used to determine the inhibitory types of alpha-amylase activity in tomato fermentation broth. The results showed that the inhibition of tomato on alpha-amylase was significantly increased after natural fermentation(P<0.05);and different dilution times,time,temperature and pH of fermentation broth had significant effects on the inhibition of alpha-amylase(P<0.05). The optimum conditions were as follows:The inhibitor and amylase acted at 33℃and pH6.8 for 10 min;the inhibition belonged to non-competitive reversible type with inhibition constant of 4.01 mg/mL. This study could provide a new way for the development and utilization of tomato and its fermented products.