In response to the phenomenon of sliding instability and failure caused by insufficient durability of lightweight soil subgrade filling materials, the structure of lightweight soil subgrade with tension anchor rods is taken as the research object. Based on elastic theory, an analytical formula for the additional stress of prestress on the potential sliding surface is derived. Combining the linear sliding surface method and the additional stress calculation method, a stability analysis method for lightweight soil subgrade with tension anchor rods is established. Through this method, the influence of different preloading stresses, panel widths, reinforcement positions, and reinforcement rows on the safety factor of the subgrade is calculated and analyzed. The analysis of the calculation example shows that the safety factor of the roadbed is positively correlated with the pre stress, panel width, reinforcement position, and number of reinforcement rows. When the pre stress increases from 0 to 100kPa, the safety factor of the roadbed increases by 12.88%; The additional stress caused by preloading on the potential sliding surface of the subgrade will have anti sliding and sliding effects, and the reinforcement effect of the subgrade is controlled by the anti sliding effect; The degree of influence of various reinforcement factors on the safety factor of the roadbed is as follows: pre stress is the highest, reinforcement is arranged several times, panel width is the second, and the influence of reinforcement position is the smallest. The research results can provide some reference for the design and construction of lightweight soil subgrade with anchor rods.