In order to control the influence on deformation parameter estimation in Excavation Deformation Monitoring when geometric observations are anomalous, mechanic information about excavation slope is considered to be unknown information, and a filtering model with unknown parameter is given. In the fixed observation window, unknown parameters do not change with time, which can be fitted with the prediction of observation residuals and residuals. At the same time, algorithm improves the reliability of the state estimations. In a real example, by using the prior geometry and physics of information to deformation monitoring, the given algorithm can significantly improve the reliability of state parameter estimation.