To solve the problems of wire network wiring interference, high equipment cost and meet the needs of large data storage and diversified data access, a system based on the internet of things (IoT) wireless network and IoT cloud platform is proposed for the remote fault diagnosis of machine tools. The system model is divided into four levels: acquisition layer, transport layer, arithmetic level and application layer. The data acquisition method based on object linking and embedding for process control (OPC) and multi-sensor fusion is used to obtain the running data of machine tools in acquisition layer; the transmission layer based on narrow band internet of things (NB-IoT) wireless communication technology and IoT cloud platform make the remote transmission, communication and storage of data come true; and the operation layer establishs diagnostic algorithm mode which combined BP neural network with expert system. Taking a machine tool spindle servo as an example, its fault phenomena is analyzed and the fault samples are obtained. The model is analyzed by error simulation, and the predicted results coincide with the expectations, which verifies the validity of the model.