Abstract: Objective To observe the myocardial protective effect of dexmedetomidine whole course pump injection for cardiopulmonary bypass valve replacement. Methods Total 140 patients underwent cardiopulmonary bypass heart valve replacement in Yiwu central hospital from August 2015 to August 2019 were selected as the research object. All patients were divided into study group(n=70) and control group(n=70) according to random number table method. All patients underwent cardiopulmonary bypass valve replacement. The study group received dexmedetomidine whole course pump injection, and the control group received the same amount of normal saline. The hemodynamic parameters such as HR, MAP and SPO₂ were recorded before anesthesia induction, after aortic opening, at the end of cardiopulmonary bypass, at the end of operation and 24 hours after operation were analyzed. The ICU stay time and hospitalization time were recorded. The cardiac rebound was observed. The levels of inflammatory factors and myocardial injury indexes were detected before and after the operation. The occurrence of adverse cardiac events was observed. Results There was no significant difference in HR, MAP and SPO₂ between the two groups(all P>0.05). There was no significant difference in ICU stay time and hospitalization time between the two groups(all P>0.05). There was no significant difference in the rate of automatic cardiac rebound between the study group(92.86%) and the control group(87.14%, χ²=1.270, P=0.260). The levels of serum inflammatory factors(TNF-α, IL-6 and IL-8) and myocardial injury indexes(CK-MB, cTnI and NT-proBNP) in the study group were significantly lower than those in the control group(all P<0.05). The overall incidence of adverse cardiac events in the study group within 30 days(12.86%) was significantly lower than that in the control group(32.86%, χ²=7.940, P=0.005). Conclusion Dexmedetomidine whole pump injection can effectively inhibit the inflammatory response, reduce the degree of myocardial injury and the incidence of adverse cardiac events.