Based on analysis of the typical system parameters of Ronchi phase shifting shearing interferometer, the main phase retrieval error sources of the interferometer are systematically studied. Combined with the traditional five-frame algorithm, retrieval phase errors of Ronchi phase-shifting shearing interferometer are analyzed and simulated with the self-designed eight-frame and ten-frame phase-shifting algorithm. The simulation results show that the ten-frame phase-shifting algorithm has a better phase retrieval accuracy than the eight-frame phase-shifting algorithm and both the two algorithms can effectively eliminate negative effects of unwanted interference from the high order diffraction light, which limits the phase retrieval accuracy. In order to improve the measurement accuracy, the following conditions should be satisfied: the phase shifting error is better than 2%, at least 10-bit quantization detector is used, the grating period error is less than 1% and the spatial coherence of light is less than 0.1. The theoretical analysis is validated by three groups of comparison experiments with different phase retrieval algorithms, shear ratios and spatial coherence of light.