Nowadays, more attentions may be paied to irradiance and temperature during the electrical performance tests of solar cell and module. But the light spectrum will also largely determine test results. During the electrical performance test, irradiance is generally traced by standard solar cell. Considering that the short circuit current (Isc) is generally used in the testing process as a basis for the irradiance calibration, and the Isc of reference cell consists of spectral distribution of light source and the spectral response of the cell together. So spectral mismatch should be analyzed from this two aspects. Natural light spectrum will be affected by atmospheric conditions and seasons, and artificial solar simulator’s spectrum is differ in thousands ways. Also because of the response wave band of the spectrum range is different, when use standard solar cell or pyranometer as the basis of the irradiance calibration, there should be respectively different results. Beyond that, two cells made of polycrystalline silicon with different spectral response may also leads to different results. We analyzed the deviation based on above factors, and discussed how to reduce the spectral mismatch deviation, then increase the accuracy of the solar cell electrical performance test methods.