Taking the photoelectric tracking and measuring system visible light camera lens as an example, through simulation analysis for the camera lens, the reason leading to the stray light spot is found. With the carrying out stray light suppression design, and comparing with the testing result of actual optical system, it's proved that the software analytical method is reliable. By building model for optical system，the scattering paths are ascertained. For each off-axis angle within 2° to 3°, stray light analysis is conducted respectively to identify the main stray light source. Comparing the result of analysis with the testing results of actual optical system, the analysis is proved to be correct. Then the structure of system is modified, and suppress stray light is suppressed. The simulation results show that when the off- axis angle is between 2.20° and 2.65°, stray light takes shape an obvious spot in the center of the image, and point source transmittance (PST) is 2.92 × 10- 4. By modifying the structure, the stray light spot is eliminated, and the PST is reduced to 3.53 × 10- 5. Stray light spot and its source, obtained through software analysis, are the same to the testing result, which proves the correctness and accuracy of the software analytical method.