Abstract: In this study, a multi-residue analytical method for determination of 11 plant growth regulators (PGRs), including uniconazole, chlormequat, mepiquat, thidiazuron, diuron, diethyl aminoethylhexanoate, flumetralin, pyraflufen-ethyl, sodium 2-nitrophenoxide, sodium 4-nitrophenoxide and sodium 5-nitroguaiacolate, in cottonseed hulls was developed based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After systematic optimization of sample preparation and instrumental parameters, the method achieved effective separation and quantitative analysis of the target compounds with different polarities. The cottonseed hull samples were hydrated with water, extracted with acetonitrile, cleaned-up by dispersive solid-phase extraction (d-SPE) with PSA and MgSO₄, then determined with HPLC-MS/MS at multiple reaction monitoring (MRM) mode, and quantified by the external standard method with matrix-matched calibration curves. The results demonstrated that the limits of detection (LODs) of 11 PGRs ranged from 0.0003 to 0.04 mg/kg and the limits of quantification (LOQs) ranged from 0.0001 to 0.1 mg/kg. The average recoveries varied from 70% to 103%, and the relative standard deviations (RSDs) were 0.30% to 13%. The method is simple and has high precision and robust stability. It was applied to analyze market samples, and the residues of 5 PGRs were detected in 13 samples. Notably, chlormequat chloride, mepiquat chloride, thidiazuron, and diuron exhibited a relatively high detection frequency, inferring that the multiple residues of PGRs are common in cottonseed hulls.