In some applications of optical phase conjugation in laser beam propagation in the atmosphere, the method of active beam light is used, in which a probe light is transmitted to the target and the reflective light acts as the beacon light. Generally, it is believed that the reflective area on the target must be small enough to be regarded as an unresolved glint, and this limits the application. In this paper, the effect of the reflective area on the optical phase conjugation is discussed, and an experiment by means of nonlinear optical phase conjugation using a ruby laser, Stimulated Brillouin Scattering is an acetone device and a hole to change the reflective area is made. We demonstrate that, the wavefront of light can be restored correctly on the target. In the case of motionless target, the limitation of the reflective area must be satisfied, otherwise the amplified phase conjugated light on the target will return to the probe light source and damage it, whereas, in the case of the remote and high speed moving target, because the reflective place on the target is changed during the period of phase conjugation, the light is only reflected on the target, and so the area may be larger than the limitation.