Obtaining the fault information online may eliminate many potential fatal accidents, in order to inspect and resolve the online fault diagnosis problem in process industry, an online fault diagnosis model based on IoT(Internet of Things) is proposed in the paper. the model is composed as four layer of user layer, application layer, basic technology layer and resources layer, and it can use the resources effectively such as virtual organizations, entity organization, equipment, network resources and so on, the basic technologies such as Internet of things, multiple information collection, knowledge engineering and application technologies were analyzed in the paper too. Finally, an application system is developed, and it proved the model is validity and correctness.