Shallow plate loading test(PLT)is widely applied in civil engineering for evaluation of subsoil bearing capacity.Side load due to soil around loading plate may influence the judgment of subsoil bearing capacity.Based on limit equilibrium theory,we derive Terzaghi ultimate bearing capacity formula under a more generalized side load distribution condition.By adjusting magnitude and distribution of side load around loading plate in PLT,we analyze side load effect on ultimate subsoil bearing capacity respectively for sand and cohesive soil foundation.Combined with an engineering case,we point out that side load effect on determination of wether allowed subsoil bearing capacity should be judged on fully consideration of soil stress state reached in the process of PLT.