DC losses have an undeniable impact on the economic and social benefits of DC transmission projects, especially in the planning stage. Accurate calculation of DC losses in DC transmission projects is an important reference for evaluating the feasibility of DC transmission projects. This article establishes a calculation model based on the principle of DC loss, and analyzes its impact on the utilization hours of DC loss in conjunction with large-scale new energy base transmission scenarios. Through example analysis, the calculation method for DC losses in large-scale new energy base external transmission projects is explained, which can provide guidance for the planning and construction of subsequent DC projects.