A method of Moire topography testing with double computer-generated gratings is proposed. It is concluded from theoretical analysis that the lateral derivative of the kernel of the projection grating being a constant is the necessary condition for the uniform accuracy testing. Under the proper designation of grating kernels, the standard model can be characterized by equalinterval straight fringes. Therefor, the defect of the tested object can be found directly and quantitatively form the deviation of moire fringe from the background pattern. Finally, computer simulations and experimental verification on the test of a torid surface are presented.