With the development of modern industry, silo diameters are bigger and bigger. Lateral pressure of bulk materials in silos is one important parameter for designing silos, which is related to the economy and safety of the structure. However, present calculation methods of the lateral pressure are mostly based on small diameter silos. For now, in the Chinese code the wall pressure computation methods are based on Rankine theory to be calculated. It is shown that the calculated results of Rankine theory may overestimate the pressure. In this paper, the lateral pressure of large diameter silos is studied. A new formula for calculating lateral static pressure on shallow silo wall is derived by static equilibrium method. The formula of this paper is simple of calculation and can be used for large diameter silos with a circular con top pile. The results agree with that of the full-sized silo experiment better than the current code.