Under the “dual-carbon” strategic background, to address the heating challenges of highway service area buildings in severe cold regions beyond urban centralized heating networks and promote the application of multi-energy complementary heating technologies integrating GSHP (Ground-Source Heat Pump), solar energy, and electric thermal storage boilers, this paper analyzes the system design and operational performance of project implementation. It explores fundamental approaches for constructing heating systems in highway service area buildings within this regional context. Selecting a case study of a 7,000 m2 highway service area building, five distinct heating schemes were designed with ground-source heat pumps assuming 80%, 75%, 70%, 65%, and 60% of thermal load respectively, aiming to determine the optimal thermal source allocation strategy. Through TRNSYS transient simulation analysis, comprehensive evaluations were conducted on solar collector performance, system COP, water supply temperature stability, and soil thermal balance characteristics across different schemes. Results demonstrate that the optimal configuration occurs when the ground-source heat pump undertakes 65% of the thermal load. This study provides valuable references for future engineering projects with similar requirements.