The working principle of the four-quadrant detector used in laser guidance is introduced. According to the technical requirements of the laser seeker and the working characteristics of the four-quadrant detector, the principle and characteristics of the optical receiving system in the seeker based on the four-quadrant detector for space positioning are analyzed. With the sequential ray tracing and non-sequential ray tracing,an optical lens is designed. Its illumination uniformity is more than 75% in the ±4°linear receiving field. Its illumination uniformity is 90% in the ±1.5° receiving field. At the same time, the spot diameter deviation of the lens in the 4 linear receiving field is less than 0.05mm. The lens design result not only meet the design requirements but also have a compact structure.The optical design method of this kind of lens is explored.