This paper expounds the functional modules and architectural forms of the building BMS system. On this basis, it points out that it is necessary to start from the overall design concept of the building, and sort out the logical relationship between the whole building intelligent project and information project step by step from the underlying subsystems, BA, BMS, big data application platform to the external docking requirements of the building. Then, according to the refined business needs and investment budget, the functional framework and external interface of the BMS platform should be set scientifically and reasonably, so as to maximize the investment value.