To make azimuth estimation to two slow-fluctuation unresolved ship targets with monopulse radar,an angle estimation algorithm based on angle bound constraint and adjustable sliding window was proposed.In the case that the ships Radar Cross Section (RCS) fluctuation obeys lognormal distribution,the monopulse responses of the two ship targets was discussed,combined with the characteristics of the real part of monopulse ratio and effect of noise.The deficiencies of unstable estimation performance and existing error of the monopulse angle estimation mean algorithm were analyzed.The target echo was selected by bound constraint of half-power beamwidth,the sliding window of the monopulse angle estimation mean algorithm was improved.Based on the selected target echo,the monopulse angle estimation mean algorithm containing the improved sliding window was used to estimate the target azimuth.Simulation results show that the proposed algorithm has stable estimation performance,and has better estimation performance than the previous estimation algorithm under the same simulation conditions,which verify the validity of the algorithm.