In this paper, optimization of the influence of the process parameters of ground source heat pump (GSHP) with the double U tube heat exchanger for space heating applications was performed. The coefficient of performance (COPsys) in GSHP system was investigated during experimental measurements with various process parameters; space air inlet/outlet temperatures (T-i(,sa) and T-o,T-sa) and soil inlet/outlet temperatures (T-i(,wa) and T-o,T-wa). Taguchi method performed for obtained the optimum process conditions on the COPsys in GSHP system. Taguchi experimental design considered as L16 orthogonal array. The most influence ofprocess parameter on the COPsys in GSHP system was evaluated by using analysis of variance (ANOVA) and signal/noise (S/N) ratio. The optimum process parameter was determined as A4B1C1D1 for COPsys in GSHP with ANOVA analysis. The optimum levels were computed as T(i)(,sa )at Level 1( )(32 degrees C), the T-o(,sa) at Level 2 (17 degrees C) the T(i)(,wa )at Level 2 (6 degrees C) and and the T-o(,wa) at Level 1 (9 degrees C) The most significant parameter on the COPsys for space heating applications of GSHP system were found as T-i(,sa) and T-o(,sa) with 48.4 %..