The surface roughness and the delamination are important difficulties in any drilling operation of (GFRP) composite materials. Both two elements cause structural integrity reduction and poor assembly as well as the potential for long-term performance deterioration. In this research, the optimization of drilling parameters using Taguchi technique, to obtain minimum both surface roughness (Ra) and the delamination factor (df). In addition, ANOVA uses to analyze the data obtained from the experiments and determine the optimal parameters in the drilling of GFRP composite materials. The results revealed that the delamination factor (df) increases with the increase of drilling speed (2250rpm-2750rpm) and increases with the increase of the feed rate (100mm/min to 125mm/min). Increasing the drilling speed and reducing feed rate can reduce the delamination factor (df) and the use of high feed rate and high spindle speed can be increasing the delamination factor (df) within the limits of specified speed and feed rates. The feed rate is the more influential factor on delamination than the other parameters. The results for very low feed rate i.e. 25mm/min and high drilling speed 2750 rpm show a clear decrease in surface roughness (Ra). Feed rate and drilling speed are the more influential factors on surface roughness (Ra) than the other parameters.