Computer simulation on heat treatment is the foundation of intelligent heat treatment. The simulations of temperature field, phase transformation, stress/strain complicate quenching operation were realized by using the model of three dimensional non linear finite element method and the treatment methods of abruptly changing interface conditions. The simulation results basically fit those measured in experiments. The intelligent sealed multipurpose furnace production line has been developed based on the combination of computer simulation on gaseous carburizing and computer control technology. More than 3000 batches of workpieces have been processed on this production line, and all are up to standard. The application of computer simulation technology can significantly improve the loading ability and relia bility of nitriding and carburizing workpieces, reduce heat treatment distortion, and shorten carburizing duration. It is recommended that the reliable product design without redundancy should be performed with the combination of the CAD of mechanical products, the CAE of materials selection and heat treatment, and the dynamic evaluation technology of product reliability. Computer simulation on heat treatment is the foundation of intelligent heat treatment. The simulations of temperature field, phase transformation, stress / strain complicate quenching operation were realized by using the model of three dimensional non linear finite element method and the treatment methods of abruptly changing interface The simulation results basically fit those measured in experiments. The intelligent sealed multipurpose furnace production line has been developed based on the combination of computer simulation on carburizing and computer control technology. More than 3000 batches of workpieces have been processed on this production line , and all are up to standard. The application of computer simulation technology can significantly improve the loading ability and relia bility of nitriding and carburizing workpieces, reduce heat treatment distortion, and shorten carburizing duration. It is recommended that the reliable product design without re dundancy should be performed with the combination of the CAD of mechanical products, the CAE of materials selection and heat treatment, and the dynamic evaluation technology of product reliability.