In this paper, we proposed a monopulse forward-looking high-resolution imaging algorithm based on adaptive iteration for missile-be detector. Through iteration, the proposed algorithm automatically selects the echo signal of isolated strong-scattering points from the receiving echo signal data to accu-rately estimate the actual optimal monopulse response curve (MRC) of the same distance range, and we applied optimal MRC to realize the azimuth self-focusing in the process of imaging. We use real-time echo data to perform error correction for obtaining the optimal MRC, and the azimuth angulation ac-curacy may reach the optimum at a certain distance dimension. We experimentally demonstrate the validity, reliability and high performance of the proposed algorithm. The azimuth angulation accuracy may reach up to ten times of the detection beam-width. The simulation experiments have verified the feasibility of this strategy, with the average height measurement error being 7.8％. In the out-field un-manned aerial vehicle (UAV) tests, the height measurement error is less than 2.5 m, and the whole response time can satisfy the requirements of a missile-be detector.