Mixed mothproofer of permethrin and tetramethrin is a new formulation for prevention cloth moth in China. A rapid and specific method is needed to simultaneously determine these two active ingredients. For this purpose, a method by GC was established with a 3% OV-101/Chromosorb WAW DMCS(180-250 microns) column at a temperature of 223 degrees C, by using di-iso-octylsebacate as internal standard. The mean coefficient of variation for permethrin and tetramethrin were 0.20% and 0.19% respectively. Linearity of detector response vs. mass concentration ranged from 0.38-2.6 g/L with r = 0.9999.