The movement of target in range direction will make the echo of scatters shift from range cell, and this will cause blur in ISAR imaging process. Thus, the envelop alignment is used to compensate this shift. However, the high resolution in WBand ISAR will cause the envelop to change its shape during the imaging period. This will cause error in traditional envelop alignment methods. Therefore, a new envelope regular method based on Keystone transform is proposed to increase the accuracy of envelop alignment. Before the Keystone transform, a target center track method is used to make the return signal coherent. The simulation results show that the peak value, entropy and contrast of image are improved by applying this method.