The construction of bridge pier foundation under the geological conditions of deep-water riverbed brings new challenges to the construction of cofferdam. In this paper, combined with the construction characteristics of the pier foundation of a super large bridge in Guizhou and the geological conditions of the site, the steel pipe pile cofferdam construction technology is used to analyze the stress of the most unfavorable working conditions of the pier cofferdam, and the pier pile cofferdam structure is designed and manufactured. The structural strength, the anti-floating and strength of the bottom sealing concrete and the overall stability of the cofferdam all meet the actual construction needs. The analysis method of this paper can provide reference for similar projects.