With the aim of conserving the Huai’an Watergate Site scientifically and reasonably, the geometrical size and structure of the site were obtained by surveying and mapping on site. Then obvious types of damage at the site were analyzed, including wall damage and wood pile damage, etc. After that, the finite element analysis method and the traditional calculation method were used to analyze the structural performance of the site, and the results of these methods were analyzed to find out hidden diseases. Finally, based on results of investigation of the actual damage and the numerical simulation, a suitable method for conservation of the site was proposed, which could provide a reference for similar masonry heritage conservation projects. The research indicates that appropriate measures should be taken to enhance the tensile strength of the wall corner during the restoration with plane turning points such as plate gates. Specific measures that could be taken for reinforcement include embedding stainless steel bars along the horizontal mortar joint.