The overall process from appearance, development to maturation of intermodal transport in America was studied around two main clues, namely technological innovation and institutional innovation. The technological innovation history included the generation of railway, the application of container transportation, the development of the piggyback transportation, the large-scale and networking application of double-layer container and so on. Meanwhile, the laws Staggers Rail Act and The Surface Freight Forwarder Deregulation Act of 1986 represented the reform of freight rates and agent system in America. About the innovation in the policy, legislation and institution system of America, the process of the interaction between technological innovation and institutional innovation, a series of laws were passed such as Intermodal Surface Transportation Efficiency Act, Agreement Rate Act of 1993 and Control Reform Act of the Truck Industry of 1994. A conclusion was made about the different function of technological innovation and institutional innovation in promoting the development of intermodal transport. Technological innovation is the foundation while the institutional innovation is the key factor in developing intermodal transport and improving its function.