In digital holography,the reconstructed optical field phase generally has high spatial variation frequency,however,the space-bandwidth product is so limited that it is easy to introduce undersampling and to cause the existence of massive unreliable data points in the wrapped phase,which makes the least- squares phase unwrapping algorithm difficult.The principle of shearing interfermetry was introduced to refactor the digital holographic reconstructed optical field.By changing the phase gradient calculation of the reconstructed optical field, the impact of undersampling was reduced.The feasibility and validity of the new method were proved by the simulated calculation and experimental verification.And the results show that the phase obtained by the new method is closer to the experimental value and it has stronger resistance ability to undersampling than the traditional method.