To address the issues of low land resource utilization efficiency in cable trench installation and poor heat dissipation in conduit trench installation, a magnetic-thermal-current multiphysics coupled finite element simulation model of a 110 kV cross-linked polyethylene cable was constructed. The current carrying capacity of both the cable trench and the conduit trench installation methods was simulated and calculated. The effects of three methods, laying concrete outside the conduit in the conduit trench installation method, using high thermal conductivity conduits, and adding backfill materials inside the conduit, on increasing the current carrying capacity of the cable were investigated. Based on the orthogonal experiment, the backfill material was improved to obtain the optimal ratio of the backfill material. The research results show that by pouring concrete outside the high thermal conductivity conduits and adding improved backfill materials with the optimal proportion inside the conduit, the current carrying capacity of the cable can be significantly enhanced. Compared with the cable trench installation method, this approach increases single-circuit capacity by 31.64% and dual-circuit capacity by 18.49%.