Abstract: Under the condition of the excavation changing from open pit into underground mine, the predictions of the ground surface displacement and the stability of slope is always the significant technology problem. In view of the insufficiency of the present prediction methods, the FLAC is used to simulate gradual excavation of No.B902 mine in Antaibao coal mine. From the case, the law of ground surface displacement is summarized, the value of displacement is predicted, and the stability of slope is analyzed. By comparing the monitoring data with the simulation results, it is shown that the FLAC is a simple and effective way to predict the ground displacement and analysis the stability of slope based on the actual physical mechanics parameters under the condition of the excavation changing from open pit into underground mine.