GSHP(Ground Source Heat Pump) system has been extensively disseminated due to the recent increasing demand of the new and renewable energy in korea. However, the system reliability has been key issues and barriers to insure a better system performance as designed originally in ISO (international standard organization) standard. This paper introduces a systematic method to verify its intended design target-so called as ISO performance data based commissioning technology for a water to air GSHP system. The commissioning technology starts from the standard ISO performance data of hybrid GSHP model and to compare its installed operation data and to calibrate by tuning to the target optimum operation parameters. Results indicated that cooling performance could be improved up to 76.6% from 46.6% from this proposed commissioning technology at the initial commissioning stage.