Directly from the theory of Kirchhoff diffraction, without any approximation about mathematical models, a series of improved digital calculation ways are used to ensure the high accuracy of OTF calculation. Through the comparative computation of several same type of softwares and typical lenses, the result shows that this software is suitable for the accurately setting the value of OTF standard lens, and also sutitable for the design and computation of verious large reltive apertures and wide angle optical systems.