A novel gravity assist space pruning(GASP)algorithm based on image tools is proposed for solving interplanetary trajectory optimization problem.Compared with traditional GASP algorithm,the concept of image is introduced to avoid missing interesting solutions with appropriate number of function evaluations.Image tools allow us to evaluate the objective function in regions in place of points and provide an effective way to evaluate the forward and backward constraints for the multi-gravity assist trajectory optimization problem.Since the interesting solutions of the interplanetary trajectory optimization problem are often clustered in a small portion of the search space rather than being overall evenly distributed,the regionwise evaluations with image tools make the little large interval with the proper Lipschitzian tolerances sampling effective.The detailed steps of the proposed method are presented and two examples including Earth Venus Mars(EVM)transfer and Earth Venus Venus Earth Jupiter Saturn(EVVEJS)transfer are given.Finally,a comparison with solutions given by the literature demonstrates the effectiveness of the proposed method. A novel gravity assist space pruning (GASP) algorithm based on image tools is proposed for solving interplanetary trajectory optimization problem. Compared with traditional GASP algorithm, the concept of image is introduced to avoid missing interesting solutions with appropriate number of function evaluations. Image tools allow us to evaluate the objective function in regions in place of points and provide an effective way to evaluate the forward and backward constraints for the multi-gravity assist trajectory optimization problem .ince the interesting solutions of the interplanetary trajectory optimization problem are often clustered in a small section of the search space rather than being overall evenly distributed, the regionwise evaluations with image tools make the little large interval with the proper Lipschitzian tolerances sampling effective. detailed sections of the proposed method are presented and two examples including Earth Venus Mars (EVM) transfer and Earth Venus Venus Earth Jup iter Saturn (EVVEJS) transfer are given. Finally, a comparison with solutions given by the literature demonstrates the effectiveness of the proposed method.