The work aims to study the convection heat transfer mechanism in the refrigerator, strengthen the convection heat transfer effect of the fluid in the refrigerator and improve the circulation efficiency of cold air. A mathematical model was established from the point of view of air outlet of the refrigerator. The internal flow field of the refrigerator was simulated by Ansys fluid analysis software, and the flow field and heat transfer mechanism in the refrigerator were studied by field synergy theory. It was found that when the angle of the air outlet was around 30°, the heat transfer efficiency in the refrigerator was higher and the temperature distribution was more uniform. At this time, the existence of the goods walls greatly changed the flow direction of cold air. After the semi-circle protrusions were added on the wall surface, the air flowed along the tangent direction of the circular arc, improved the degree of synergy between speed and temperature gradient, enhanced the convection heat exchange in the refrigerator from the angle of speed field, temperature field and their interaction. The overall heat exchange efficiency was increased by 38.65%. It was concluded that the cause of fluid flow and heat transfer in the refrigerator was the fluid disturbance. The change of air outlet angle and the presence of protrusions enhanced the disturbance of the goods to fluid. The combined action of the two changed the distribution of the inner field of the refrigerator, and improved the overall refrigeration efficiency of the refrigerator. The research can provide reference value for the factory production of refrigerated cabinet.