Abstract: In order to determine the structural safety of steel structure engineering, and to evaluate whether the construction results meet the design, it's necessary to apply the real-time monitoring of the stress and deformation of the main structure members in the construction process. Thus we have designed and developed an automatic real-time online monitoring system for the stress and deformation, and applied the system in the steel structure project of Hangzhou International Expo Center. The application results shows that the system is stable in operation, with reliable data and high precision, which effectively guides the project construction, and ensures the quality and safety of the structure in the construction process.