A weigh-in-motion (WIM) for a single container system based on tandem container was proposed. First， the composition structure of hardware in this system was introduced，and WIM model was established. Next, RBF neural network was used to simulated WIM model, and then a self-adjusting algorithm of gravity migration was founded. Finally, a WIM software for a single container with Visual Studio 2010 was developed. This software was simply operated and pragmatic, and also the efficiency of WIM was improved. In the whole system, model-building, data collection, Algorithm simulation, data storage, selection and printing were realized, and error ration of this system was less than 3%, therefore it has better business prospect in practice.