Abstract: An efficient parallel algorithm to accelerate the calculation of the far-fields was proposed and implemented for solving the electric large antenna radiation problem, based on the upward pass or the aggregation phase of the parallel multilevel fast multipole algorithm(MLFMA). According to the geometry tree structure of the parallel MLFMA, an efficient hybrid MPI-OpenMP parallelization algorithm was designed with the direct aggregation of coarser level far-field radiation pattern and parallel in-row interpolation. The computation of far-field radiation pattern and antenna gain of the extremely large parabolic reflector of FAST by this algorithm shows the accuracy and efficiency of the parallel program, compared with the computation by the equivalent current direct integration method. The numerical results demonstrate that the presented approach has good accuracy for the radiation characteristics, and the computational efficiency has improved about ten thousand times for single direction under same far-field calculation task compared to the equivalent current direct integration method.