Abstract: Phase shifting interferometry enjoys a wide application in optical precision measurement. However, the common phase extraction algorithm is vulnerable to phase stepping errors of the phase shifters. The former least square iterative phase extraction algorithm can suppress the influence of phase stepping errors ，but it takes long time. We presented a high-efficiency least square iterative phase extraction algorithm based on selective sampling. Firstly the interferogram pixels were sampled with an equal interval to reduce the calculation time; Next the low quality pixels were filtered out based on the interference contrast to prevent the phase error from growing; In the experiment, when the sampling interval was set to 2, the proposed algorithm took only 0.725 s, compared with the 6.687 s of the former iterative method, and the discrepancy of phase shift was only 0.032 9. The experiment verifies that the proposed algorithm can greatly reduce the calculation time with little compromise of phase extraction accuracy, which is highly suitable for highspeed phase shifting measurement applications.