In order to achieve to detect a variety of physiological signals form ECG ( electrocarcliogram)monitoring signal, reducing the complexity of the monitoring equipment, according to the impact of breathing motion on the ECG, it presents a respiratory information extracted from the ECG (ECG-derived respiratory signal, EDR) algorithm. First, according to Pan & Tompkins algorithm extracted from the ECG R-wave, and then, using a natural cubic spline interpolation algorithm to estimate the baseline ECG and remove baseline wander, getting clean ECG, finally, get clean ECG R-wave, the use of natural spline interpolation algorithm is applied to obtain R wave amplitude modulation signal which contains respiration information. In paper, it selected Fantasia database, which in addition to providing the ECG signal, it also gave a breathing signal synchronized recording. It used Matlab software to verify the proposed algorithm, associated analyzed and compared. The simulation results showed that the algorithm mentioned in this paper can extract the respiratory
signal from ECG. By comparing with respiratory data in the database simultaneously recorded, it confirmed the validity of the algorithm.