The theoretic solutions of position characteristic of one-dimensional PSD irradiated by a moving light source were presented based on a distribution RC transmission-line approximation.From three facets,such as scanning speeds of light source,starting position and gradient angle of the scanning track,position characteristics of one-dimensional PSD were analyzed.Results show that when the light source scans continuously the PSD surface in the uniform rectilinear movement,output photocurrents are independent of y component of the scanning speed.And in the initial scanning course,the true incident positions of light can not be correctly detected by PSD.The computed incident position of light approaches to the true position as long as the lower scanning speed,the close starting position to the origin of the coordinate system or the greater gradient angle with X axis are obtained.