In this paper, a unit of NC machining process used tooling automatic storage stereo library tunnel stacker due to no corresponding fault warning system, when the equipment is running in the process of failure, the maintenance staff often need to spend a lot of time and effort to determine the cause of the malfunction And deal with, seriously affecting the production of the normal production of the product site problems. Based on the existing hardware and software conditions of the equipment control system, a set of on-line early warning system for automatic stacker storehouse based on S7-300 and Wincc flexible 2007 operating environment was developed, which realizes real-time warning of equipment failure information online, Greatly improving the efficiency of equipment maintenance staff to deal with equipment failure to ensure that the normal production of enterprise products.