The key is detection of QRS complex in the analysis of ECG signal. Wavelet transform is used to analyse ECG signal. ECG signal is filted by digital filters，and the QRS complex can be distinguished from noise. baseline drift. and high P or T waves. Adaptive amplitude thresholds are employed to make final determination whether the detected event is a QRS complex. This alogrithm has been used in a microcomputer-based medical instrument-Intelligent Multichannel Analyser(mode GKD-405A) The QRS detection rate is above 98%.