The adaptive multi-null monopulse principle of phased array radar， derived from the maximum likelihood estimation, was introduced. It was found that the failure of double-null monopulse technique in multiple group targets was caused by a large iteration step. In order to optimize the iteration in angular estimation, a method of weighted step was proposed. By the proposed method, an accurate angular estimation of multiple group targets was achieved with a few computations. Several simulation results demonstrate that the angular estimation error of three targets is about 0.15 beamwidth in medium signal to noise ratio. However, the performance will get worse when there are a large number of group targets or the phase offset of echoes is closed to 0.