In this report, we introduce a new wave-equation method of migration velocity analysis (MVA). The method is based on the linear relation that can be established between a perturbation in the migrated image and the generating perturbation in the slowness function. Our method consists of two steps: we first improve the focusing of the migrated image and then iteratively update the velocity model to explain the improvement in the focusing of the image. As a wave-equation method, our version of MVA is robust and generates smooth slowness functions without model regularization. We also show that our method has the potential to exploit the power of residual prestack migration to MVA.