According to image plane interference status of optical aperture synthesis(OAS) and Huyges Fresnel theory, a mathematical method is set up which fits with the true condition. By dividing telescope mirror into many small fragments with pinhole interference conditions, OAS image plane interference formula is deduced according to fragments interference with each other, and OAS image plane interference computer simulation is done. The influence of wavefront tilt and optical path difference is analyzed and simulated in the end.