OBJECTIVE： To evaluate effects of dexmedetomidine hydrochloride on cardiovascular response of middle aged and elderly patients during tracheal extubation period. METHODS： 110 general anesthesia patients with colorectal cancer were collected and randomly divided into observation group and control group， with 55 cases in each group. All patients received general anesthesia with same dose. Observation group was given intravenous pump of dexmedetomidine hydrochloride 0.5 μg/kg after surgery， and control group was given intravenous pump of propofol 0.5 μg/kg. HR and MAP of 2 groups were compared 10 min before tracheal extubation， at the moment of tracheal extubation， 5 and 10 min after tracheal extubation. The oxygen saturation of blood， the time of respiration recovery， opening eyes and extubation were recorded in 2 groups. RESULTS： There was no statistical significance in HR and MAP between 2 groups 10 min before extubation and 10 min after extubation （P＞0.05）. HR and MAP of observation group were significantly lower than those of control group at the moment of extubation and 5 min after extubation， the levels of HR and MAP were significantly increased in the 2 groups with statistical significance （P＜0.05）. There was no statistical significance in oxygen saturation of blood， the time of respiration recovery and extubation between 2 groups （P＞0.05）. The time of opening eyes in observation group was significantly shorter than in control group， with statistical significance （P＜0.05）. CONCLUSIONS： Dexmedetomidine hydrochloride could significantly decrease cardiovascular stress response and shorten recovery time of middle age and elderly patients with colorectal cancer  during tracheal extubation period.