Abstract: When analyzing a large reflector antenna with antenna array as its feed, it is difficult to realize the overall solution using full-wave algorithm because of its large electrical size. At the same time the antenna unit usually has complex structure, material and feeding mode, and therefore the high-frequency algorithm is unable to ensure sufficient calculation accuracy. To solve this complex electromagnetic problem, first the full wave algorithm is used to extract the subarray equivalent sources, and the radiation characteristics of the antenna array can be fast calculated by translating the equivalent sources. Then the near-field method is used to calculate the coupling effect of the antenna array on the reflector, and fast algorithm is used to calculate the reflector. Both the antenna array and the reflector are calculated using parallel computing technology, which greatly improves the computing efficiency. Numerical result verifies the effectiveness of the method. At the same time, the radiation problem of a large parabolic cylindrical antenna is effectively solved by the method.