Abstract: In order to improve the time-consuming problem of shaped reflector antenna optimization and design，an effective analysis technique for computing far field patterns of shaped reflector antennas is presented and the far field patterns of shaped reflector antennas is analyzed in this paper. The integration area is converted into a unit circle on the projection from antennas surface，with two dimensional trapezoid -compound Gauss formulas，the integral equation is converted into the form of numerical summation. The far field patterns of shaped reflector antennas with different caliber in C-band and X-band are considered. The result agrees well with that of direct integration and Gordon integration. The computational efficiency is proved and the validity of the proposed approach is verified.