Abstract: Distortion compensation of high resolution range(HRR) profiles plays an important role in ISAR imaging of space target with high speed.Since the ambiguity function′s peaks of space target baseband echo lay on a cluster of parallel lines which contained the original,a multi-objective programming model was established based on the constraint bounds of the line cluster.After that,an analytic algorithm for velocity estimation was presented with the application of regularization principle.Furthermore,an iterative searching algorithm was applied to minimize the entropy of HRR profiles and a velocity estimator with higher precision was provided,where the proposed analytic solution was set as the initial value for iteration.Simulations demonstrate that the proposed hybrid searching strategy takes the advantages of analytic algorithm and iteration algorithm in the computational complexity and estimate precision,which can effectively estimate the velocity of space target and compensate the distortion of HRR profiles.