In order to study the effect of the fire on the workers, the PyroSim was used to simulate the fire of in grain reserve storages in this paper. The widely used warehouse was selected as the research object, and the physical model was established. Aiming at the fire scenario caused by phosphine fumigation port, the development of fire smoke and temperature distribution were analyzed, and preventive measures were proposed. The results showed that the formation stage and upward development stage of smoke are the best time for fire fighting and evacuation of operators, and the smoke has not diffused to the entire warehouse. And the operators should evacuate immediately when the smoke diffuses at the top. The operators are forbidden to enter the warehouse when the smoke fills the warehouse. The temperature of the warehouse below 1.5 meters does not reach the limit of the personnel endurance range between 10 seconds and 100 seconds. And due to the full combustion of the combustor, the temperature keeps rising, and the operators are facing the risk of burns in 100 seconds to 10 minutes.