Urban geological information platforms have traditionally focused on static data provision for public service, constrained by funding and limited engagement with engineering applications. This study takes Hangzhou—a major Chinese megacity—as a model to propose a technically integrated platform that aligns with urban infrastructure development, particularly underground space engineering. Through the adoption of the large-scale relational database system Oracle, we first established a comprehensive storage framework for fundamental urban geological and underground infrastructure information, thereby completed the construction of the core databases. To ensure spatial consistency across multi-source data and to meet the platform’s high computational demands while improving overall server responsiveness, we introduced three critical innovations: voxel-based model encoding, distributed computing, and frontend-backend separation with asynchronous processing. To align with urban engineering projects and enhance economic returns, the platform was initially developed through the integration of foundational geological data, including borehole records and aboveground-underground spatial information. Based on this foundation, its practical application in Hangzhou’s Qiantang New Town further demonstrated the platform’s potential in supporting subway routing, underground structure planning, and engineering cost analysis. Consequently, the construction of the Hangzhou geological information platform not only offers robust support for urban decision-making and smart city development but also provides a replicable model for addressing the technical and institutional challenges commonly encountered in the development of urban geological platforms.