Abstract: To evaluate the safety of SYP- 9625 in Citrus grandis‘Guanxi miyou’, study the residual degradation dynamics of SYP-9625, we designed 2 treatments of bagging and no-bagging, sprayed SYP-9625 once with the recommended dose or double recommended dose, and determined the residues by HPLC-MS/ MS. The results showed that: there was a good linear relationship (r2=0.9997) in the range of 0.4-400 μg/L of SYP-9625, and the detection limit (LOD), there coveries and there lative standard deviations (RSD) was 0.06μg/kg, 84.2%-90.0% and 5.6%-8.4%, respectively; the residual degradation dynamics of SYP-9625 accorded with the first order kinetic equation (k 0.1444-0.2271), and the half-life (T1/2) of bagging and no-bagging treatment was 3.56-4.80 days and 3.05-3.50 days, respectively; SYP-9625 degraded more slowly in bagging treatment, and the residue of SYP-9625 was not detected in all final products 65 days after the application.