This research mainly inforduces air conditioning system of the typical Beijing Jianguomen underground rail transportation hub for study. Based on Navier-Stokes equations and widely used standard k-ε turbulence model, it established computational fluid dynamics model for solving the flow field in urban underground rail transportation hub. Use computational fluid dynamics field simulation software ANSYS CFX as calculation tool, it established the physical and mathematical model of underground rail transportation hub. The boundary condition sets based on lots of literature. Based on the results of simulation, temperature and velocity distribution of typical sections can be displayed. The simulation also shows temperature and velocity of key location.