The laser four-quadrant location system has the advantage of small-size and high-precision. Aiming at the disadvantages of structure-complicated, large weight and high-cost of traditional laser four quadrant location optical system, the Fresnel lens is used to take the place of the ordinary lens. Based on the principle of laser four-quadrant location optical system, effect of spot illumination distribution on ratio between four-quadrant’s deviation signal and the azimuth angle is analyzed, conclusion that only the spot whose centre illumination is lower than edge illumination could meet the ideal liner relation is obtained. The design method of ideal laser four-quadrant location optical system is given, a four-quadrant location optical system which can testify the analysis result is designed using this method. The ratio between deviation signal and azimuth angle of simulation result could approach a constant value.