Abstract: Phase unwrapping is one of the key processing steps during reconstruction the digital elevation model from the signal of interferometric synthetic aperture radar(InSAR) or interferometric synthetic aperture sonar(InSAS). In order to solve the problem of low unwrapping efficiency with large interferogram, we propose a blocked minimum discontinuity phase unwrapping algorithm in shared memory environment. The whole phase quality map is computed firstly through multi-cores of CPU, then wrapped phase image and phase quality map are tessellated into small regular blocks, which are unwrapped by the quality guided and minimum discontinuity optimization method simultaneously. In the end, the minimum discontinuity optimization process is performed again on the border of different blocks and the low quality areas located on the border to get the final merged unwrapped result in the main thread. Tests performed on the simulated and real InSAS interferogram show that the speed up reaches 3.98 and 2.26 respectively.