In this paper we introduce a method for integrating multiple data sources to construct higher-precision electronic maps. We comprehensively utilize engineering construction data conforming to rail transportation design specifications, GNSS data, and LiDAR data. Initially, we independently establish electronic maps using engineering construction data and GNSS data. During the GNSS-based map creation process, we employ Bezier curve fitting to smooth the route trajectory. Subsequently, we perform inter-frame matching with laser point clouds, using positions and orientations acquired from the same mileage locations on both maps as initial values for registration. Finally, the registration result with the higher score is chosen as the corrected trajectory, and this process is repeated along the entire route to obtain a global map. Comparing the map constructed in this paper with the one constructed using solely GNSS data, significant improvements are evident both in overall trends and local details. The ROI (Region of Interest) area constructed using this map accurately depicts the clearance space during the train’s journey.