Monitoring surface deformation is crucial for the early warning of landslides, facilitating timely preventive measures. Triboelectric nanogenerator (TENG) demonstrates great potential for self-powered distributed monitoring in remote and power-scarce landslide areas. However, landslides deform typically at a rate of a few millimeters per day (mm d−1), making it challenging for TENG to directly monitor the deformation process. Herein, a method for monitoring surface deformation of landslides by constructing an ultra-low-speed triboelectric displacement sensor (US-TDS) is reported. Utilizing a force storage-release device and an accelerator, the US-TDS can produce obvious sensing signals at a linear input speed of 4.32 mm d−1. The coefficient of determination (R2) for the fitting curve of the pulse signals within the speed range of 21.6 to 129.6 mm d−1 reaches 0.999. Moreover, US-TDS can detect deformation displacement as small as 0.0382 mm. The stability of US-TDS displacement measurements is confirmed at a speed of 108 mm d−1, with relative errors under 1%. Ultimately, a real-time monitoring and early warning system for landslide surface deformation is constructed and verified through a combination of indoor simulations and outdoor experiments. This work provides a feasible solution for the scientific monitoring and early warning of the landslide development.