Abstract: The Goldstein branch-cut method is a traditional method for phase unwrapping. Its phase unwrapping result is easily affected by phase residues caused by noise and discontinuous phase flaws in practice. To characterize effect of discontinuous phase on unwrapping algorithm, after simulating a data base for discontinuous phase, unwrapping was studied with Goldstein branch-cut phase unwrapping method. The effect of the residual phase on the size of the searching window radius was focused on specifically. The unwrapped phase was compared with the actual phase. The results show that accurate unwrapped phases can be obtained in situations with one and two disjointed discontinuity flaws. Accurate unwrapping phase results cannot be obtained in situations with two crossing phase discontinuous flaws. Good results can not be obtained for two crossing phase discontinuous flaws. Different discontinuous phase flaws have different effective branch cut searching window radius. There is an effective searching window radius for the Goldstein branch-cut approach. Those results can provide reference to research of the phase unwrapping only and jointly with Goldstein branch-cut.