Abstract: An analytical method was developed for residue determination of monosultap in tomato, cucumber and soil samples by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Firstly, monosultap was hydrolyzed to nereistoxin under alkaline condition. Then, after liquid-liquid partition with ether, the organic layer was evaporated and restructed in methanol. The formed nereistoxin was detected by UPLC-MS/MS, and the residue of monosultap could be calculated accordingly. Results showed good linearity ranging from 1 to 500 μg/L with correlation coefficients higher than 0.99; the limit of detection (LOD) was 0.213 μg/kg (tomato matrix), 0.212 μg/kg (cucumber matrix) and 0.172 μg/kg (soil matrix), and the limit of quantification (LOQ) was 0.710 μg/kg (tomato matrix), 0.707 μg/kg (cucumber matrix) and 0.573 μg/kg (soil matrix). For tomato, cucumber and soil samples, average recoveries ranged from 79% to 101% at spiked level 10,100 and 500 μg/kg, and the relative standard deviations (RSD) was between 6.6% and 16%. The developed method is suitable for determination of monosultap total residues in tomato, cucumber and soil samples.