The construction of deepwater pile foundation is one of the important working procedures of bridge construction.It is necessary to build the fixed aquatic construction platform in order to construct the bored pile.So the construction platform must be scientifically designed and reasonably built,and it is very important to ensure the safety and stability of the platform in the whole course of building and working.Take the example of cast-in-place bored pile engineering for a large reservoir bridge,the mechanical behavior of the fixed aquatic construction platform braced by steel tube pile is analyzed with ANSYS software,the key technique is studied,and some conclusions are obtained that will be helpful to the similar engineering works.