Effect of kieselguhr on enantioselectivity of enzymatic hydrolysis of chiral dichlorprop methylester (2,4-DP) has been specifically studied by chiralgas chromatography. The results show that the adsorption of lipase on kieselguhr greatly enhanced enantioselectivity of hydrolysis of 2,4-DP with ER increasing from 1.58 to 5.31. It triggered changes in conformation of the enzyme, thus affecting the microenvironment of active sites, which may be the major reason of enhanced enantioselectivity of enzymatic reaction. Due to adsorption on kieselguhr, lipase became harder to combine with R-2,4-DP and the reaction rate of hydrolysis decreased. On the other hand, it was easier for S-2,4-DP to get close to the active sites of lipase, so the rate in 2 creased. In addition, adsorption of the pesticide on kieselguhr decreased "free pesticides", which also enhanced the enantiose-lectivity of hydrolysis of 2,4-DP.