In the common-optical-path single-photon laser ranging system, there is a phenomenon that the laser emission moment overlaps the echo photon receiving time, which is called the main wave/echo signal overlapping. Overlap causes the loss of echo signals during a specific ranging period, resulting in a decrease in the probability of target detection. In this paper, the conditions for the occurrence of the main wave/echo signal overlapping phenomenon are studied by analyzing and calculating the structure of the ranging system and time sequence of signals in ranging. The correlation between the flight time of the ranging photon and the overlapping phenomenon is obtained. The mechanism of laser emission adjustment on overlapping is described, and a countermeasure for the main wave/echo signal overlapping based on the periodic adjustment of the laser emission time interval is given. Based on this, the corresponding overall simulation and ranging experiment are carried out, and the results show that the proposed method can avoid the occurrence of main wave/echo signal overlapping to a certain extent and improve the detection probability of the target.