Recently,computational fluid dynamics(CFD) has been used extensively in many fields of industry along with the development of the computer science and fluid mechanics theory.In this paper,the unsteady numerical simulation in the doorway was done by CFD,the temperature field in the doorway of a minitype cold store was analyzed.The space of the influence on the cold store by the environment was also discussed.The unstesdy temperature field in two 20s' periods of opening and closing door was simulated,it's found that the natural flow caused by the density differences is the major flow of the air around the door.It was also found that the temperature field in the downside recovered quickly,but that in the upside was not as fast as it.It needs 20 seconds to get back the initial condition.The result shows that the simulation can reflect the reality well.