To treat sudden arrhythmias often happened in cardiosurgical operations, e.g., atrial fibrillation, ventricular fibrillation and ventricular tachycardia, it was necessary to develop special low-energy cardioverter-defibrillator with precise energy measurement and impedance compensation, working in both epicardial manner and endocardial manner. The system consisted of 4 main parts: cardioverter-defibrillator module, R synchronization module, impedance detector and power supply module. High-voltage circuit was isolated from low-voltage circuit to insure the security. The System could discharge with biphasic truncated exponential waveform rapidly; precision of R wave identification was high; impedance classification compensation could be fulfilled; discharge energy measurement was precise. So the system has the ability for cardioversion and defibrillation in both epicardial and endocardial manner in cardiosurgical operations.