The obvious echoes of the side-lobe transmitting waves are caused by the transmitting antenna working on the condition of a stimulation pulse with abnormal pulse width. The studies of the properties of the echoes are significant in theory and applications on the GPR. Based on the ratio of the electric field intensity from the echoes of the side transmitting waves to the total receiving electric field intensities, a method of the echoes of the side-lobe transmitting waves is presented. The results obtained from an application with this method are compared with the trial data. The comparisons show that the agreement between the echoes acquired using this method and the trial data is good. The rationality of the method is approved.