Abstract: To ensure the precision of pesticide application and reduce the loss of agents, the relationship between liquid surface tension and maximum liquid hold-up (R_m) of apple leaves was established by adjusting surface tension with four common surfactants and using interfacial tensiometer, microgravity balance and plant canopy scanners. Moreover, a method for early evaluation of application amount was provided for fruit trees using common canopy parameters. The result showed that the R_m of apple leaves on both adaxial surfaces in the early growth stage was significantly higher than that at the later growth stage. In the same growing period, R_m of apple leaves on the abaxial surfaces was higher than that on the adaxial surfaces and R_m decreased with the increase of the leaf inclination angle. In the early growth stage, the influence of surface tension on the R_m of apple leaves on both abaxial surfaces was greater than that on the abaxial surfaces. With the increase of leaf inclination angle, the influence of surface tension on R_m of apple leaves on both abaxial and adaxial surfaces decreased. When the concentration of liquid did not reach the critical micelle concentration (cmc), the surface tension of liquid was positively correlated with the R_m of apple leaves. The maximum dosage of pesticides in fruit trees could be estimated according to the established linear regression equation and canopy parameters such as the average leaf inclination angle, leaf area index, and canopy shadow area. Four pesticides were used to verify the practicability of the method. These results can provide a theoretical foundation for estimating the application amount of pesticides and reducing the loss of agents in apple orchard.