Abstract: To address pain points such as data silos, interface conflicts and low efficiency in the traditional file-level collaboration mode for railway engineering investigation and design, this paper developed a five-in-one data collaboration technical system featuring "unified standards, centralized storage, service sharing, task-driven processing and multi-layer reuse" to support the digital and intelligent transformation of the industry. This system established a full-dimensional collaboration standard system covering project coding, storage management and interactive transmission, and built a unified data lake with classified governance, designed dual static and dynamic data service interfaces together with a registration and verification mechanism, proposed a task-driven closed-loop flow method, and realized global data and capability reuse via microservices and layered encapsulation. This research yielded 24 categories of professional specifications, 466 data tables and more than 300 shared services. A collaboration system developed on this basis was applied on a large scale. The application results show that the system achieves a paradigm shift from file-level to data-level collaboration, improves collaboration efficiency by more than 87%, and effectively breaks down professional data barriers. It provides key technical support for the digital transformation of railway engineering investigation and design.