Abstract: The existing phase-unwrapping algorithms are analyzed and classified, aiming at solving the problem of under-sampling in wrapped-phase map. The least-square algorithm based on lateral shearing interferometry is studied. Four common phase-unwrapping algorithms are applied to the wrapped-phase map of Lygodium japonicum cell, which is obtained by image-plane digital holography recorded with spherical reference waves. The results show that the least-square algorithm based on discrete cosine transform and the pre-condition conjugate grads algorithm result in transfer of phase-unwrapping error in the under-sampled area;the quality-guided path following algorithm results in pull phenomenon and island area because of the residual point without recognition, and its processing is slow;the least-square algorithm based on lateral shearing interferometry has the best effect for dealing with the under-sampled wrapped-phase map, and its processing is the fastest.