Abstract: The study was aimed to observe poisonous side reaction after using Radix glycyrrhizae with Radix knoxiae of the Chinese ＂anti-18＂. The mice were assigned into five groups. The mice in the group Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴand CK were fed Radix glycyrrhizae decoction, Radix knoxiae decoction, dividual decoction of Radix glycyrrhizae and Radix knoxiae, admixture decoction of Radix glycyrrhizae and Radix knoxiae, and physiological saline, respectively, for 3 d. Spontaneous activity and fatality were recorded. The mice were executed after 72 h, and blood was collected for determination of glutamic-pyruvic transaminase level. Pathological section was prepared, and routine blood, liver/body ratio and kidney/body ratio was determined. The results showed that Radix knoxiae had a certain impact on liver function. Radix knoxiae compatible with Radix glycyrrhiza aggravated the impact on liver function but had no impact on kidney function. It also had effects on forms of liver and kidney organization, but they could recover after drug withdrawal.