To establish a system of effective bioassays for natural acaricides against three mite species, influences of bioassay system, solvent drying time, and leaf-dipping time were investigated. Among the tested organic solvents, including diethyl ether, hexane, and acetone, acetone was found to be the most suitable for developing natural acaricides, whereas diethyl ether and hexane were not suitable. Solvent drying and leaf-dipping times of acetone were suitable at 10 min and 60 s, respectively. Application method of spraying (direct contact) bioassay was more effective than other methods. These results could be used in the standardization of bioassay systems for natural acaricides.