To study the characterization of five kinds of CYP450 in the liver of cold syndrome rats and the regulative effect of heat traditional Chinese medicine.Methods:Cold syndrome model was induced in SD rats for 21 days by gavage of Anemarrhena asphodeloides-Gypsum Fibrosuum-Cortex Phellodendri-Gentiana scabra.In addition,cold syndrome rats were treated with Cinnamomum cassia extract to prepare the treatment group.Saline was used as the control medicine.The liver microsomes were prepared by calcium precipitation method,incubated with mixed probe drugs,and the percentage of metabolic elimination of the probe drugs was determined by HPLC method to evaluate CYP450 activity.Total RNA was extracted from the liver and mRNA expression of CYP450s was determined by real-time fluorescent quantitative PCR.Results:The cold medicine can inhibit the activity and mRNA of CYP3A1 in rats.Cinnamomum cassia has a certain regulative effect which took place at mRNA level.Conclusion:This study should be further combined with protein expression experiments to evaluate and verify the characteristics of CYP450 enzyme in cold syndrome and the regulation effect of heat traditional Chinese medicine from multi-angle system.