Abstract: GC combined with pre-column derivatizaiton was used to determine formaldehyde in eraser. After being crushed to the size of 0.180 mm, 2.0000 g of sample was extracted with 20 mL water at 70 ℃ for 20 min and cooled, and then extracted ultrasonically for 30 min. After centrifugation, 10.0 mL of the extract derivatized with 0.5 mL of 2,4-dinitrophenylhydrazine at 70 ℃ for 15 min. The solution was cooled and then extracted with 5 mL of toluene for two times. The extract was separated on a DB-5 chromatographic column and formaldehyde derivative was detected by electron capture detector. The linearity range of formaldehyde was 0.105-10.5 mg·L^-1 and the detection limit (3S/N) was 0.01 mg·L^-1. Recovery rates obtained by standard addition method were in the range of 88.6%-92.4%, and RSDs (n=6) was 2.1%. This method was applied to the determination of formaldehyde in 32 kinds of erasers, giving results in the range of 0.135-48.5 mg·kg^-1.