Indoor airflow is an important factor affecting indoor thermal comfort and human health; it is also an important consideration for architectural design, ideal living environments, and green building fields. Currently, most building models required for indoor airflow simulation have been manually created by researchers, which is inefficient and error-prone in modeling. To overcome this problem, this study examines the similarities and differences between the general standard data model Industry Foundation Class (IFC) in the BIM (Building Information Model) and the spatial grid required for indoor airflow simulation and proposes a conversion method from an IFC model to spatial grid. This method uses the rich semantic, geometric, and relational information in the IFC model to automatically extract building interior space, divide numerical calculation grid, and map semantic attribute information to the spatial grid. On this basis, an integrated simulation framework is constructed with OpenFOAM to simulate the airflow movement of the indoor space of the building. The simulation results show that the method used in this study can automatically construct the spatial grid using existing IFC models without re-modeling, which provides important support for indoor airflow modeling. In addition, the integrated simulation framework connects model construction, simulation analysis, and other steps through tool chain. This process simplifies the simulation operation, provides convenience for indoor airflow simulation, is conducive to the wide use of indoor airflow simulation in architectural design and architectural design optimization, and also provides reference for related numerical simulation research and digital city modeling.