This study investigates the modularization and standardized design of connection joints in integrated prefabricated box buildings to address various issues present in current box building systems. By analyzing the development and current state of modular buildings both domestically and internationally, a new type of box building joint system is proposed. Standardized designs are applied to various components of the modules, and different combination forms of standard modules are developed. The study introduces the application of these designs in existing engineering projects. Finally, finite element simulation technology is used to examine the impact of connection corner thickness on the joint bearing capacity. The results indicate that increasing the thickness of the corner joints can significantly enhance the load-bearing capacity, and specific recommendations for optimizing thickness are provided. This research offers theoretical foundations and practical guidance for the development and wider adoption of modular box buildings.