Currently prestack time migration technology has been extended greatly,while the application result of post stack time migration is even more effective than that of prestack migration because of the high calculation efficiency and low S/N ratio in some place. So the authors consider that post stack time migration should not be abandoned completely but the proper migration methods should be chosen according to the characters of seismic data. Aiming at some western area with low S/N ratio ,three usual methods of poststack time migration are chosen for experiments.The experiments validate the relative merits and applicability conditions of these migration methods and provide reliable reference to how to choose proper migration methods.