The annual operating characteristics of a photovoltaic/thermal (PV/T)-coupled ground-source heat-pump (GSHP) system with cross-seasonal heat storage for an office building in Jinan were investigated via on-site testing combined with TRNSYS and GeoStar simulations. For a ten-year operation period, the ground temperature and energy efficiency of the coupled and single GSHP systems were compared and analyzed. The results showed that the integrated energy efficiency ratio (IEER) of the coupled system exceeded 1.5 during the heating/cooling seasons, peaking at 2.21. The renewable energy fraction contributed by the PV/T components was highest during the transition season, peaking at 0.9 in April. In summer, the injected heat from PV/T inhibited the performance of the heat pumps, and the coefficient of performance (COP) and the IEER were 10.5% and 4.97% lower than those in winter. Over the ten-year operation period, for the coupled system, the soil temperature decreased by 0.13 ℃, IEER decreased from 1.24 to 1.22, and the renewable heat fraction decreased from 0.459 to 0.443. For the standalone GSHP system, in contrast, the soil temperature decreased by 0.7 ℃ and the IEER decreased from 1.195 to 1.15. The PV/T-coupled ground source heat pump system achieved soil thermal balance regulation and coordinated optimization of cooling, heating, and power, thus providing an efficient and sustainable clean energy solution for cold regions.