Abstract: An apparatus and method for detecting and processing an impedance rheogram includes a constant current source with output electrodes, an impedance signal detecting circuit having detecting electrodes, an ECG signal detecting circuit having detecting electrodes, a signal processing circuit and an output device. The impedance signal detecting circuit and ECG signal detecting circuit respectively, defect the impedance signal and ECG signal, the signal whereby processing circuit divides the impedance signal into cycles according to an R wave sequence, then performs linear interpolating for each cycle and in-phase superposing-averaging for a certain number of cycles, and restores the impedance waveform according to a predetermined number of interpolating points used for each cycle, so as to automatically trace arrhythmia and eliminate respiration interference to the impedance rheogram.