Abstract: This paper took a highway in Guilin as a study case, chose TDR monitoring technology as a major research tools and used ANSYS to simulate the TDR to monitor the entire process, based on the comprehensive analysis on the existing early warning technology of the karst soil cave along highway covered area. The simulation results show that it may cause damage to ground surface if there is soil cave with a diameter of more than 3.0 m in the earth layer, which is 5.0 m or so away from the bed rock surface. If the layer thickness(5.0m) and beam cross-section size(8 cm × 6.5 cm) remains unchanged, ground deformation will be more obvious, and the deformation will presents as a slow linear trend, as the soil cave is growing upward slowly along the bed rock surface and its diameter keep on increasing. If the soil cave is 2.0 m long and 4.0 m deep, or it is 4.0 m long and 3.0 m deep, beam deformation tend to stability when it is buried at 2.0 m to 4.0 m depth. If the soil cave is 3.0 m long and 3.5 m deep, beam deformation are almost the same when it is buried at a depth of 1.0～3.0 m. If the soil cave is 5.0 m long and it’s roof is 2.5 m deep, beam deformation, which is 6.74 × 10-2 m and 6.75 × 10-2 m respectively, are basically the same when beam buried at 1.0m and 2.0m depth, which is also mean that it has reach the limiting equilibration.So it can more effectively monitor the soil deformation and the hole evolution trend that monitoring beams are laid within a depth of 2m from the roof of soil cave.