To improve the safety level of large and heavy freight transportation, and to improve the efficiency of rail freight transportation, an automatic out-of-gauge identification system for large and heavy freight has been developed in the present paper. The developed system adopts information including the three-view drawing of the freight and the user specified type of train vehicle, and then performs comprehensive analysis to obtain three-dimensional structure of the freight by comparing with the gauge of railway, which at last results in the automatic out-of-gauge identification technology for freight loading. The system can help choose train vehicle before transport of goods, and provide the level of out-of-gauge to ensure the safety of the transport.