OBJECTIVE： To explore the transform of the medicinal properties of Coptis chinensis-Cinnamomum cassia couplet medicines before and after mixing. METHODS： Mice were randomly divided into normal group， weak constitution （induced by food restriction and swimming） group， weak constitution+C. chinensis group， weak constitution+C. cassia group， weak constitution+couplet medicine group， prosperous constitution （induced by high protein diet） group， prosperous constitution+C. chinensis group， prosperous constitution+C. cassia group and prosperous constitution+couplet medicine group， with 10 mice in each group. After modeling， each group was given relevant medicine intragastrically by 20 g （crude drug）/（kg·d）， and normal group was given equivalent volume of normal saline intragastrically for consecutive 7 days. The proportion of rats remained in high-temperature areas was recorded. Organ index， biochemical index （Na+/K+-ATPase， Ca2+/Mg2+-ATPase）， total antioxidant capacity （T-AOC）， SOD activity， the serum content of noradrenalin and dopamine were detected. RESULTS： Compared with normal group， proportion of mice in high-temperature area increased in weak constitution group， while liver index， spleen index， renal index， biochemical index activity or content decreased （P＜0.05）； the change of above index in prosperous constitution group were opposite to weak constitution group； above index had statistical significance except for the proportion of mice in high-temperature area （P＜0.05）. Compared with weak constitution/prosperous constitution group， the proportion of mice remained in high-temperature area and liver index increased in weak constitution/prosperous constitution+C. chinensis group， while biochemical index activity or content decreased （P＜0.05）； the change of above index in weak constitution/prosperous constitution+C. cassia group were opposite to C. chinensis group， spleen index and renal index increased （P＜0.05）； the proportion of rats remained in high-temperature area increased in weak constitution/prosperous constitution couplet medicine group， and biochemical index activity or content decreased， among which total antioxidant activity decreased significantly （P＜0.05）. CONCLUSIONS： The couplet medicine manifests the “cold nature” after C. chinensis and C. cassia equally paired， because “hot nature” degree of C. cassia is lower than “cold nature” of C. chinensis.