Prediction on the deformable body of unstable rock block is a main measure to actualize disaster prevention and mitigation for the collapse hazard. With a view to the basic model of kalman filter method and its character in the data processing of deformation monitoring and based on the state vector for the deformation body of unstable rock block, the prediction model of unstable rock block was established. In addition, the prediction model was validated based on the monitoring data of unstable rock block in Mo-zi Ridge, Three Gorges Reservoir Area. Calculation results indicate that the average error value is less than 1mm and to predict the displacement of unstable rock block by using kalman filter method has a preferable effect.