A solid phase extraction/high performance liquid chromatographic method was developed for the analysis of residues of 24-dichlorophenoxyacetic acid(24-D),gibberellic acid(GA3),paclobutrazol(PP333) and 6-benzylaminopurine(6-BA) residues in watermelons.Samples were extracted with 80% methanol water solution,then concentrated and cleaned up on a Strata C18 solid phase column.The separation of target compound was carried out on a ZORBAX Eclipse XDB-C18 column(4.6 mm×150 mm,5 μm) under gradient condition using methano-0.15% phosphoric acid as mobile phase.The ultraviolet detecter was used to detect analytes at 220 nm.Four plant growth regulaters were qualitatively analyzed by using retention time and UV spectra,and quantitatively determined by the external standard method.Under the optimal conditions,the calibration curves were linear between the peak areas and the concentrations in the range of 0.5-10 mg/L with correlation coefficients(r) more than 0.999.The limits of detection were between 0.05 mg/kg and 0.15 mg/kg.The recoveries at two spiked levels of 1.00 mg/kg and 3.00 mg/kg ranged from 82% to 90% with relative standard deviations(RSDs) no more than 3.8%.The results indicated that this method was simple,accurate and sensitive,and was suitable for the analysis of 24-D,GA3,PP333 and 6-BA in fruits.