The anchoring angle of prestressed anchor rods is an important parameter that affects the support effect of lattice anchoring systems. A reasonable anchoring angle of prestressed anchor rods can provide more effective support effects. Taking the BP2 landslide in Qingdao Huanglaoan as the research object, four working conditions were designed based on different environmental conditions: self-weight, earthquake, extreme rainfall, and extreme rainfall earthquake. The Midas GTS NX finite element software was used to establish its numerical simulation model, and analyze the slope stability coefficient, stress, deformation changes, etc., under different working conditions and anchor rod anchoring angles. Thus, the optimal design formula for the prestressed anchor rod anchoring angle of the lattice anchoring system can be obtained. Then, maximizing the support effect of the lattice anchoring system can provide reference for the parameter optimization design of the lattice anchoring system for landslide deposits.