Ground source heat pump (GSHP) system are widely recognized as an energy-efficient renewable energy utilization system, particularly for public buildings. In the GSHP systems where multiple units operate jointly, the control strategy for these units plays a key role in enhancing energy efficiency. This study proposes a novel control strategy for the joint operation of multiple heat pump units under varying load conditions, using a hotel building in Xi'an and an office building in Harbin as illustrative examples. The proposed control strategy was analyzed and compared with traditional average load method. The simulation results demonstrate that the proposed control strategy significantly improved the average coefficient of performance (COPs) of GSHP units and reduced the total energy consumption of the systems applied in both of the studied cases, by raising average part-load ratios (PLRs). The proposed control strategy effectively meets the buildings' load demand while simultaneously decreasing system energy consumption, thereby offering significant practical engineering value in terms of energy savings for the air conditioning systems.