Abstract: 4-Aminoazobenzene was separated from polyester textile sample by accelerated solvent extraction (ASE) with acetone under the condition of 120 ℃ and 10.34 MPa. The extract was evaporated to dryness at 35 ℃ and the residue was dissolved in 2.0 mL of methanol. NaOH solution and sodium dithionite solution were added to reduce 4-aminobenzene. The solution was cooled to room temperature and extracted with methyl tert-butyl ether. The supernatant was taken and used for GC-MS analysis, using HP-5MS capillary column for GC separation and EI (70 eV, 230 ℃) with mass scanning range of 35-350 amu in MS analysis. It was found that mass concentration of 4-aminoazobenzene in the range of 1.0-150.0 mg·L-1 kept in linear relationship with values of corresponding peak area. Value of lower limit of determination (10S/N) was found to be 5.0 mg·kg-1. Test for recovery was made by standard addition method, giving value of av. recovery of 70.2%. Values of RSD′s (n=6) found were less than 4.5%.