In this study, an actual hybrid GSHP system equipping with acooling tower, which is installed in an office building of Shaox-ing, is real-time monitored from Nov. 2012 to Mar. 2015. Basingon the monitoring data which have been processed by DM tech-nology, a post-evaluation procedure is conducted to evaluate theperformance of this GSHP system. The main operation problemsin this GSHP system are pointed out. Then this hybrid GSHP sys-tem is modeled by a DM algorithm, which is the most appropriate algorithm selected out from six classical sorting algorithms under different operation modes and each operation mode is respectivelymodeled by optimal algorithm. Follow that, the average long-termper formance of this hybrid GSHP system is predicted and evalu-ated under different operation modes by those data-driven models.Besides that, the relationship between long-term performance andshort-term performance of GSHP system is discussed and the majorfactors which directly affect the results of short-term assessmentare analyzed. Finally, the optimal time and number of days whenconducting a short-term monitoring with the purpose of predictingthe long-term performance of a GSHP system are provided.