Photoelectric insolation meter may have large errors when measuring scattered radiation under sunny and cloudy weather conditions due to their shading design. In order to reduce the measurement error, the reflection direct radiation error and diffuse distribution error of the four-, six-, and eight-divided shading scheme under different weather conditions are analyzed by TracePro simulation, and it is concluded that although the six-and eight-divided shading scheme can detect the dome of the sky in a better way, the increase in the number of the shading holes will result in the difficulty of correcting the diffuse distribution error. Therefore, this paper establishes a diffuse distribution error correction model for the four-divided shading scheme, and verifies its validity through simulation and actual measurement. After the correction, the correlation between the scattered radiation received by the total radiation sensor and the radiation measured by the scattering sensor is significantly improved, with the Pearson correlation coefficients above 0.95 , and the average relative error reduced to below 4%. In the actual test, the monthly cumulative error of the photoelectric heliometer was reduced from 12.25% to 2.66%, significantly enhancing measurement accuracy.