Objective To present a method based on wavelet transform for detecting the QRS complexes of electrocardio-gram(ECG) without preprocessing.Methods By comparing three different kinds of wavelets,the first derivative of Gaussian function wavelet whose coefficient of wavelet is more sensitive adopted for MIT-BIH Arrhythmia Database which is widely and internationally accepted in the end.The catastrophe points of QRS complexes are detected by time-frequency analyz-ing.Results The method is proved to be precise and effective by applied to detect the QRS complexes of the ECG record provided by MIT-BIH.Conclusion The method is satisfied real time of ECG monitoring system and has preferable potential application.