Abstract: Based on WinCC and Web Service, this paper introduces a fault alarm system with S7-1200 PLC as its controller. Through collecting and analyzing the key data, the system can grasp the operation status of the equipment in real time, especially the key is to enable the system to have the ability of early warning, to detect abnormal trends in time, and to facilitate the management personnel to deal with them in time. The system adopts PROFINET bus and Web Service communication technology, which has the advantages of simple operation, high automation and high reliability.