Abstract: In order to study the law of freeze-thaw induced deformation of the slope support of open cut tunnel sec? tion in seasonal frozen area under the coupling effect of stress field, temperature field and moisture field, the FLAC3D finite difference software is used to analyze the failure of slope support with shotcrete and anchor bolts for the open cut tunnel section of the Jiaoxi tunnel. The result shows the temperature field and excavation slope are the important factors affecting slope stability; the deformations of slope support are different under different temperatures but the deformation law is the same; the largest deformation induced by frost heave and thawing settlement occurs at the slope shoulder and the deformation fluctuates greatly near soft rock and soil; the optimal excavation slope is 1∶1 in terms of satisfying stability and economic rationality under freeze-thaw effect. The research results are consistent with the measured ones, which shows the instability evaluation model can predict the safety state of slope support of open cut tunnel accurately and scientifically.