In-situ attenuated total reflection FTIR (in situ ATR-FTIR) was used for the dynamic research on the residual of pesticide. The in-situ characterization of dichlorvos and orthene on the tomatoes' surface shows that the dichlorvos has obvious volatility and its degradation amount is 80% 20 minutes after spraying. Meanwhile, the ATR-FTIR shows that the strong absorption peak of dichlorvos at 1 734 cm(-1) turns to negative peaks and the absorption peaks at 3 073 cm(-1) significantly abate. The absorption peaks at 1 277 cm(-1) become weak and red shift (30 cm(-1)) shows that the dichlorvos may be hydrolyzed to some extent. While the absorption peaks of orthene show no change 120 minute after spraying. It shows that the orthene is relatively stable.