Structural Health Monitoring system - SHMs has been playing a vital role in monitoring large - scale structures during their performance in a lifetime, especially with the long - span bridge, such as a suspended bridge or cable - stayed bridge. In a SHM system, many kinds of sensors are used to set up at the specific locations in order to monitor and detect any changes of structures in real - time based on the changes of monitoring data as well as the changes of correlation among monitoring data types. This paper proposes a method of applying the correlation and regression analysis for processing the displacement monitoring data acquired by GPS - RTK considering the effects of environmental factors such as temperature and wind - speed. The results show that the air - temperature has high correlation with the displacements of a cable - stayed bridge acquired by GPS - RTK measurement along to specific directions while the wind - speed has low correlation. Then the general displacement of the target bridge could be recognized and regression equation is also built to predict the bridge displacement under effects of the air temperature.