Abstract: This study takes the Xiamen Second East Passage Project as an example to deeply explore the key technologies for high-precision construction of large prefabricated cross sea bridge beams. The project construction faces multiple challenges such as large tidal range,fast flow velocity,and complex geological conditions,which require extremely high requirements for waterproofing technology and construction accuracy. For this purpose,this study has developed core construction technologies such as high-quality prefabrication of large piers and abutments,highprecision installation of large piers and abutments,and high-precision installation of large section steel box girders.The innovative application of these technologies not only forms a high-precision bridge construction technology system suitable for complex construction environments,but also provides strong technical support for the smooth progress of the main bridge project of Xiamen Second East Passage,enabling it to be opened for operation 5 months ahead of schedule.The results of this study not only enrich the technical reserves of bridge construction in China,but also provide valuable experience for the high-precision assembly construction of future large-scale cross sea bridges.