Abstract. Rockslides are a common and devastating problem affecting mining and other engineering activities all 11 over the world; consequently, there have been many studies into their prediction and prevention. This study focused 12 on a recent rockslide in an open pit mine in Liaoning province, China. The stability of the rock slope under 13 excavation and rainfall conditions was monitored using an efficient real-time monitoring system. A further 14 numerical analysis was performed using the Finite Element Method with Lagrangian Integration Points (FEMLIP), 15 and the normalized global second order work was implanted to assess the structure instability as a safety factor. In 16 fact for the future it would be very interesting to compare in real time measurements and simulations, and not only 17 to develop back computations after failure. The numerical results indicate that the rock slope remained stable during 18excavation, yet lost stability after subsequent rainfall. Water infiltration, along with a major geological discontinuity, 19 degraded the strength of the weak zone and induced the rockslide. The monitoring approach presented its robustness 20 and generality, and was worth being generalized. The numerical approach proposed the evolution of the safety factor, 21 comparing the monitoring data, and the mechanism of the rockslide was determined. It could be used as an assistant 22 tool for the disaster predictions. 23 24