In the research of phase shifting methods in ESPI,two new kinds of improvement algorithms about phase shifting are presented to reduce the interference of high frequency terms in speckle pattern during phase caculation.In order to prove the reliability of the improved phase shifting algorithms,typical beam is measured by using ESPI and improved phase shifting algorithms.The experimental results are offered.The beam is also caculated by using finite element method(FEM).The comparison between experiment and caculation shows that the improved phase shifting algorithms are effective in ESPI