Abstract: The surface tension and its components,the surface free energy of cucumber and tomato leaves and the contact angle on cucumber and tomato leaves of pyrimethanil SC were measured by using optical contact angle measuring device.The results showed that the surface tension of different formula of pyrimethanil SC was around 39-51 mN/m,and the dominant component in surface tension was dispersion,the formula added SC-4 showed the lowest surface tension(39-48 mN/m);The surface free energy of cucumber and tomato leaves was about 22 mJ/m2,which was not conducive to liquid wetting,and the dominant component was polar force;The contact angle of different formula on tomato leaf ranged from 51° to 86°,and that on cucumber leaf ranged from 30° to 62°,suggesting that pyrimethanil SC was more easily adhered to cucumber leaf.The formula added 7227-A showed the best wettability on cucumber leaf,and the formula added SOPROPHOR FD showed the best wettability on tomato leaf;The results of field trial indicated that the liquid wetting properties were positively related to its field efficacy.The results showed that the wettability of pyrimethanil SC formula was not only related to surface tension,but also to its components,and was influenced by target surface properties,Using the wetting properties of the liquid on the target to analyze and evaluate its efficacy was feasible.