Abstract: The disturbance of the surrounding soil by tunnel excavation will inevitably lead to surface settlement. When calculating the surface settlement caused by tunnel excavation, various prediction methods have assumed that the tunnel convergence mode is bilaterally symmetrical. This assumption ignores the influences of asymmetric convergence of the tunnel, and the resulting surface settlement is also symmetrically distributed. In order to predict the surface settlement caused by a bias tunnel, a new tunnel bias convergence mode is proposed, and the corresponding bias parameters \theta , \gamma _1 and \gamma _3 are defined. Based on the stochastic medium theory, a prediction model for the surface settlement caused by the bias tunnel is obtained using the coordinate transformation and double-integral numerical processing. Through actual engineering cases, the applicability of this method is verified, and the influences of the relevant parameters on the surface settlement are analyzed. The proposed model extends the traditional symmetric convergence mode to asymmetric situations, can well predict the asymmetric trend of surface settlement, and it is closer to the monitoring values of actual cases.