A piezoelectric deformable mirror for phase compensation is designed and fabricated and its piezoelectric properties are ex situ characterized by using the Fizeau interferometer. Moreover, an iterative global optimization algorithm is developed to realize a quick and accurate approach to the target figure. The in situ phase compensation performance of the mirror and its ability to optimize the focusing spot size are verified under the focusing beam mode and with the hard X-ray speckle scanning metrology. The experimental results show that the focal spot size is compressed from 43.4 μm to 12.9 μm after phase compensation. The research here lays a foundation for the realization of rapid phase compensation in the Shanghai Synchrotron Radiation Facility.