As a main bearing structure of suspension bridges, the stability of anchorage foundation is very important. For the north-anchor foundation of the Run Yang Bridge, the stabilities against sliding and overturning are analyzed from the computation results of three-dimension finite element simulation models. The effect of soil resistance before and behind the pit on the stabilities is analyzed. Suppose the values of overload cable tension increase proportionally and by studying changes of the deformation and stress of anchor foundation, the basement resistance and the foundation stabilities against sliding and overturning with different overload coefficients, overload safety is obtained for anchor foundation. Based on the numerical computational results of the stability and overload analysis, some beneficial results are obtained for the stability analysis of anchorage foundation of suspension bridge.