To address the issues of the current nodal pricing mechanism, which does not incorporate fixed transmission costs and leads to unfair transmission cost allocation, this paper proposes a full-cost electricity pricing model based on power flow tracing technology. By defining full-cost electricity pricing and integrating generation marginal costs with effective transmission costs, the proposed model adheres to the principle of "costs borne by beneficiaries." The effectiveness of the proposed model is validated through case studies on IEEE 30-bus and IEEE 118-bus systems. The results demonstrate that the proposed method can optimize power grid resource allocation and enhance investment efficiency while considering power grid congestion.