Abstract: It is important to forecast hourly operation characteristic for design and strategy evaluation of ground-coupled heat pump system (GCHPs). Based on the basic heat transfer principle of ground heat exchanger (GHE), this paper presented a fast forecast method for operation characteristic of GCHPs by comparing with the G function method for the superposition of heat transfer rate corresponding to different contribution of each time step. In order to validate the method, the annual hourly calculated results were compared with the sample results of the GCHPs based on the finite het source model outside the borehole and quasi-three dimension heat resistances inside the borehole. Result showed that the relative errors of characteristic parameters were all less than 1% and the computation time was only 1/1000. This study is helpful for the design and application of GCHPs.