Objective To investigate the effects of dexmedetomidine and propofol on hemodynamic indexes, blood gas indexes and cardiac function in patients undergoing heart valve replacement. Methods From September 2021 to August 2024, 83 patients with heart valve replacement under extracorporeal circulation (CPB) in our department were selected. After entering the operating room, all patients received routine ECG monitoring and anesthesia induction, and were divided into the control group by convenient sampling method. After endotracheal intubation, propofol emulsion injection (5 mg/(kg·h)) was injected intravenously with constant speed pump] and observation group [42 cases were given dexmedetomidine hydrochloride injection (0.4 μg/(kg·h)) on the basis of control group]. After deep anesthesia was achieved, routine anesthesia was maintained and surgical treatment was performed. Perioperative indexes, hemodynamic indexes, blood gas indexes, cardiac function, operative indexes and adverse reactions were observed in 2 groups. Results The observation time of cardiac recurrence, recovery, extubation and ICU in the observation group were shorter than those in the control group (P < 0.05). The mean arterial pressure (MAP) and heart rate of the two groups decreased first and then increased, and the MAP and heart rate of the observation group were higher than those of the control group at all time periods (P < 0.05). Arterial oxygen saturation (SatO2), oxygen partial pressure (PO2) and PH value were increased in both groups, and the observation group was higher than the control group (P < 0.05). The partial pressure of carbon dioxide (PCO2) was decreased in both groups, and the observation group was lower than the control group (P < 0.05). Left ventricular ejection fraction (LVEF), stroke output (SV) and cardiac output (CO) were all increased in both groups, and the observation group was higher than the control group (P < 0.05). Left ventricular end-diastolic volume (LVEDV) was decreased in both groups, and the observation group was lower than the control group (P < 0.05). There was no statistical significance in the incidence of adverse reactions between the two groups (P > 0.05). Conclusion The use of dexmedetomidine and propofol in patients with heart valve replacement is beneficial to the stability of hemodynamic and blood gas, promote the recovery of postoperative cardiac function, improve the perioperative indexes of patients, and have high safety.