In order to study the stress and deformation characteristics of the PLC construction method pile cofferdam structure, this paper takes the deep-water foundation construction of a certain project as the background. The main bridge of the project adopts (90+180+90) m continuous beam arch, and the lower structure of the main bridge adopts a bearing platform and pile group foundation. The plane size of the cofferdam is 29.8mx22.35m, the overall cofferdam is composed of steel pipe piles, Larsen VIW shaped steel sheet piles, purlins, and internal supports. Using finite element software to establish a comprehensive model of the cofferdam space, considering the effects of load combinations such as soil pressure, static water pressure, water flow force, and wave force on the cofferdam, it is divided into 5 working conditions for loading calculation according to different construction stages, and the most unfavorable working conditions are obtained. The structural stress and deformation of the cofferdam are analyzed. The results indicate that the strength and deformation of the deep-water foundation cofferdam meet the requirements. The lateral deformation at the center of the cofferdam structure shows a trend of first increasing and then decreasing. For the purlin and internal support system, the force on the lower support is greater than that on the upper support, and the force on the middle position is greater than that on the two ends. To ensure safe construction, the lower purlin and internal support can choose steel with larger moment of inertia and yield strength.