Based on the state-of-the-art studies of solar-soil source heat pump compound system,operation patterns of solar-soil compound system were analyzed,particularly the advantages of parallel operation pattern.It is found that parallel operation pattern is better for solar-soil compound system.Furthermore,the heat balance issue of solar-soil compound system was emphatically analyzed from four aspects,which were annual analysis of heating and cooling load,the heat exchange of ground heat exchanger,capacity determination of solar-assisted heat source and heat balance calculation of solar-soil compound system.Moreover,annualrate of heat balance in a solar-soil source heat pump compound system was calculated with a case study.It is shown that the annual heat unbalance ratio is 19％,which is less than 20％.As a result,the practical solar-soil compound system can basically maintain the heat balance of soil.