Abstract: At present,the application of building information model(BIM) in projects is becoming more urgent in China,however the massive model of BIM with jumbled data seriously restricts the use of BIM technology in practical applications. Large BIM models have the problems of slow loading and stuck display in the display process. Therefore,it was proposed to build a BIM lightweight system,and provided a review and browsing platform for a large number of BIM models by self-developed BIM simulation system platform. Four methods were used to build BIM lightweight system,geometric simplification algorithm,rendering optimization algorithm,file format optimization and data structure design. The triangular surface of BIM model was optimized by edge folding algorithm. According to the model of multi-source heterogeneous data,the file format and data structure were designed. At the rendering level,the combination of PagedLOD technology and geometric simplified model,the double-thread method of rejection and rendering,and the rendering optimization technology of batch rendering were researched and implemented independently to complete the preliminary construction of BIM lightweight system and verified it in the platform. The results showed that the application of lightweight method system made the platform quickly load a large number of BIM models and smoothly display them,and had ability to display multi-source heterogeneous data models on the same platform