Phase unwrapping is widely applied in a variety of fields including optical and microwave interferometry, adaptive optics, synthetic aperture radar and image processing. A phase unwrapping method is developed based on simulated annealing. The local behavior of the unwrapped phase is approximated by a plane. The parameters of the plane are optimized by simulated annealing. Computer simulation and experimental results make it clear that this method can effectively remove noise in phase map, unwrap the wrapped phase, and reconstruct the surface of the detected object.