Compared with magnitude value, phase of MRI signal is more prone to be influenced by motion. A novel method, sensitivity constrained phase update (sCPU) was proposed for robust and efficient ghost artifacts reduction. Using coil sensitivities as constraints, a synthetic image can be generated in which the ghost is reduced due to phase cancelation. Phase error was first estimated from the raw image and the synthetic image, and then was used to update the phase of raw k-space. The results with simulated and in-vivo data show that the ghost artifacts can be efficiently reduced after several iterations.