Abstract: To improve sparse reconstruction effect caused by unknown number of targets and mesh mismatch in group target scene, an improved sparsity adaptive matching pursuit (SAMP) algorithm was designed for target detection of frequency agile and pulse repetition interval (PRI) jittered radar. First, improving the atom selection strategy in the backtracking stage, selecting atoms with similar energies through regularization for grid mismatch correction, the algorithm was arranged to effectively reduce the reconstruction error and suppress the reconstruction spurious peak. Then, adaptively expanding the search step (group target number estimation) according to the power change rate of the reconstructed signal, the algorithm was arranged to speed up algorithm search. Simulation results show that, comparing with SAMP and traditional group target detection algorithm, the improved SAMP algorithm can improve reconstruction effect and reduce the target range and velocity estimation error.