Abstract: In order to study the residue degradation dynamics of cyromazine on vegetable soybean and conduct its safety assessment, liquid chromatography and field test were applied to analyze the residue amount. The results showed that the initial residue amounts of cyromazine on vegetable soybean were different in different pesticides application schemes. When the concentration was 375 g a.i./hm2, the initial residue amount was higher than that of 187.5 g a.i./hm2. When spraying cyromazine twice at 7 days interval, the initial residue amount was more than that of just one time spraying. The residue degradation dynamics of cyromazine on vegetable soybean was in conformity with the first-order kinetic equation, T1/2 was 5.6-6.1 d and T0.99 was 37.3-40.6 d. In the final residue test, cyromazine was sprayed for 187.5 g a.i./hm2 with the conventional method, spraying only one time and twice at 7 days interval, and after 15 days of the last application, the final residue amount of cyromazine was 0.132-0.194 mg/kg and 0.156-0.202 mg/kg, respectively, which could meet the requirement of MRL (0.5 mg/kg) in GB 2763—2014.