Abstract: In this paper,the development of PSD in land and abroad are briefly introduced,and some experiments for the study of the effects of the light source on the position precision of PSD are performed as well.It is proved that the fluctuation of the light intensity can lead to the loss of the position precision of PSD,the results are far from those derived from theoretical analysis:there is no effect of light intensity on the position precision.At the same time,the experiments also show that the size and shape of the light speckle can also exert certain effects on the ultimate position precision.