According to the disadvantages of traditional Foucault test, the wavefront retrieval technology of off-axis aspheric surfaces is proposed. According to the mathematical analysis of Foucault test, a mathematical model is established and the wavefront integrating algorithm is proposed to reconstruct wavefront of the off-axis aspherical surface through integrating gray values of two Foucault pattern, removing tilt of wavefront map, and wavefront integration etc. When the circles of confusion in two directions reach to 0.152 mm and 0.284 mm, the surface error tested by interferometer is that PV value is 1.110 μm and RMS value is 0.194 μm, and the wavefront patterns are consistent. Experiment proves that the technology of wavefront retrieval is correct and can be used to guide the manufacture of off-axis aspherical surface until to be coherent with interferometer test of the fine grinding stage.