In this paper, the effect of differential filter on joint power spectrum has been analyzed and so-called power spectrum differential filter is introduced. The function of this filter is real with some peculiarity, so it is easy to make. Computer simulations indicate that the performance of power spectrum differential filter joint transform correlator (JTC) is improved obviously than that of a classical JTC in the areas of peak intensity, Peak-to-sidelobe, half correlation width and so on. It will greatly enhance the reliability of pattern recognition. The experimental result is agreement with that of computer simulation. A new parameter is introduced in this paper that can discribe correlation better.