Objective: To study the influence of Xinmailong injection (XML) on the isolated thoracic aorta of rats in different states.Methods: A cumulative dosing method was utilized to evaluate the influence of XML on the isolated thoracic aorta of rats in resting state, and KCl or noradrenaline (NA) induced contracted state.Different tool drugs were used to analyze the mechanism of the effects.Results: Compared with the control group, a specific concentration range of XML could excite the isolated thoracic aorta in resting state, further increase the vascular tension after KCl action, while decrease the vascular tension after NA action.The vasodilative effect of XML on blood vessel after NA action was inhibited by propranolol and diclofenac, while showed no influence from Nω-Nitro-L-arginine.Conclusion: XML has different effects on the isolated thoracic aorta of rats in different states, and the mechanisms of the effects are related to calcium channel, β-receptor and prostaglandins.