The effect of temporally partial co herent on noise performance of a whit light optical signal processor is presented. The output signal-to-noise rate (SNR) is used a9 a means of measuring noise performance of the proposed whitelight processing system. The noise sources considered are the grain-noise and phase-noise at any plane in the system. The result shows that the set-up noise can be restrained and the output SNR can be improved considerably by using broad band temporally partial coherent illumination.