Abstract: Remote real-time monitoring system for landslide hazard can realize the monitoring of the opposite relation between slope sliding force and resistance force by changing the anchor cable prestress set in the slope.The setting distance of anchor cable is correlated with the influence scope of prestress.Reasonable distance not only can implement effective monitoring on the slope stability,but also can avoid the occurrence of multi anchorage effect so as to minimize the investigation.According to this problem,the paper,taking engineering conditions of a certain open-pit mine as background,builds the operation models by using the Lagrange algorithm and makes corresponding analysis,and thus determines the relation between the influence scope of prestress and the length of anchor cable,presenting the critical value when multi anchorage effect is approaching.The analysis conclusions provide evidence for the setting of slope stability monitoring mechanical system.