Filter optimization design method of photoelectric integral light source color illumination instruments is introduced. The design error is caused by the beam oblique incidence which leads to the filter spectral transmittance different from that under of normal incidence. The diffuse incident colored glass transmittance correction model is established. The model is applied to the color illuminance measurement instrument design. Experiments are designed to verify the matching results, and the experimental results demonstrate that the correction model reduces the design error effectively.