Abstract: The influencing factors for earth pressure and its distribution on retaining wall are studied by analyzing comprehensive observed data of temperature, displacement and earth pressure of retaining wall of Yixing Pumped Storage Hydropower Station. The calculated parameters are determined through back analysis of the observed data. An imitative analysis of temperature stress on retaining wall is performed. The effects of the height of rockfill, displacement of retaining wall and air temperature on the earth pressure on retaining wall and its distribution are studied by means of the FEM numerical calculation. It is indicated that the air temperature is an important influencing factor for the distribution of earth pressure on retaining wall when the rockfill has no change. The earth pressure mechanism and the reason of periodic change of earth pressure on retaining wall during operation are further revealed.