An algorithm based on the wavelet transform (WT) was developed to analyze the QRS complex in a three-dimensional magnetocardiogram (3-D MCG) recorded from 3 normal subjects and 1 patient with anterior myocardial infarction (MI). By using a wavelet equivalent filter constructed with the WT algorithm, the high frequency components of the QRS complex related to the late fields (LF) were detected for the patient with anterior MI at different scale. We quantified the high frequency components of the QRS complex by calculating root-mean-square (RMS) value at different scale. The LF mainly existed in the frequency band of about 35.5 to 110.5 Hz with the amplitude of about 0.1 to 0.4 pT for Bx, By, and Bz components. In order to discuss the activities of the heart between the normal subject and the patient with anterior MI, we have also evaluated the spatial energy distribution (SED) of the QRS complex by displaying isoenergy contour maps at different scale. Being different from the normal subject, the patient with anterior MI represented different the pattern of the SED in various frequency band for the ST segment of the QRS complex of Bx, By, and Bz components. It is efficient to use the WT algorithm for analyzing the QRS complex in the 3-D MCG.