In order to increase the accuracy and robustness of phase unwrapping, a novel stair phase unwrapping algorithm was proposed. This algorithm combined the gray and phase coding to unwrap the phase. The algorithm based on gray can project different gray intensities to determine different levels. However, when the period was small, there was little difference between intensities which will generate phase errors. Phase unwrapping based on phase had great robustness but it occupied the computation. Compared with traditional method, the creative point of this method was that it designed two encoding methods for phase unwrapping. The first type of pattern was based on grey information that separated the global modulation grating. The second type of pattern was based on phase coding. The experimental results show that the algorithm can determine the level of the wrapped phase accurately and the 3D information can be obtained quickly.