To ensure the safety of the rock slope excavation of the G336 Shenmu section ramp, a remote monitoring system based on BeiDou-3 navigation satellite system (BDS-3) was designed and used to monitor the slope in real time. The monitoring system can realize real-time remote automatic deformation monitoring, which is composed of data acquisition and transmission subsystem, BDS data calculation subsystem and data release management subsystem. Through slope excavation simulation, it is found that the cumulative horizontal and cumulative vertical displacement of the slope rock and soil are both less than 5 mm, and the daily variation of the dis-placement is less than 3 mm. For construction safety, the cumulative deformation warning value and the daily deformation warning value are set as 4 mm and 2 mm respectively. By monitoring the deformation of the excavation process, it is found that more changes are indicated in the vertical displacement of the rock and soil of the slope than the horizontal displacement. The vertical displacement can firstly reflect the state and trend of the displacement of the slope. Therefore, more attention should be paid to the vertical displacement, in order to ensure construction safety. The sudden change of slope soil displacement can be used to judge whether the slope is stable, when strength reduction method is used to analyze slope stability. However, no sudden displacement feature is shown at the slope foot, the monitoring point should be selected in the upper part of the slope or near the plastic belt, as far as possible.