In order to realize the intelligent calculation of cost management during the implementation of construction projects, this paper proposes a methodological architecture based on Multi-intelligent Reinforcement Learning (MARL) and Building Information Model BIM. The construction cost management problem of the project is analyzed with examples in order to optimize the construction cost management and construction time management of ZZYH comprehensive business building. The results of the study show that a reasonable rebar path can be found through 40 independent simulation verifications, and the final convergence reaches 100%. Compared to manual savings, the collision-free rebar design using the computational framework of BIM and multi-intelligence saves roughly 90% of the time. In terms of optimizing the construction cost management of civil engineering, installation engineering, cable engineering, and overhead line engineering, the total amount of cost savings of the project amounted to 382,320,000 yuan.