Taking a largest-scale drainage pump gate built for operation in Shanghai as an example, the material mechanics method, the combinatorial algorithm of material mechanics and rigid body balance, and the finite element method are used to calculate and study the stress concentration phenomenon of the base stress of folded-line baseplate in soft soil area is studied at the folded place. The stress distribution characteristics of base stress of the folded-line baseplate are analyzed ad obtained. Through the sensitivity analysis of the base stress under the different upper loads, the folded-line inclination, subgrade elastic modulus and other influencing factors, the change law is summarized, which provides a reference for the optimization design of similar engineering structures.