Abstract: An autoclave geometry model used for manufacturing composites was established, the flow field and temperature field for autoclave under idling state were numerically simulated, and the simulated results of flow field were compared with the results available in literature. The results indicate that the appearance of the plate mold would change the distribution of flow field in the autoclave, making the velocity decrease between mold and air duct, while the velocity near the air duct and mold increase. Along the direction of air supply, the temperature of the mold surface changed quickly on the left side than that of on the right side. Temperature gradually reduced from door to tail of the autoclave in overall distribution trend. The using of the fan could enhanced the heat exchanges between the mold and the air, making the temperature of the mold close to the temperature of the air more quickly. Flow field simulation results are agree well with results in literature, verified the reliability of simulation results.