Abstract: In tunnel deformation prediction, the grey model can be used to only predict the general trend of tunnel deformation, not to reflect the volatility caused by prediction errors. Therefore, early warning for tunnel deformation is difficult. In order to address the shortcomings of grey theory regarding the prediction of soil tunnel deformation, a grey theory with upper and lower bounds was put forward, and the upper and lower bounds in grey prediction were defined by processing the prediction errors in the grey model. With a given prediction zone, this method improved the grey prediction form (point by point) in time-series, providing warning time for tunnel deformation. Meanwhile, according to the intersection forms of the deformation control lines, grey limit curves, and grey midline, the safety levels regarding soil tunnel deformation were classified so that the safety of soil tunnels can be estimated more reasonably.