Now-a-days glass fiber-reinforced plastics (GFRP) are always applicable in variety of engineering applications. It is used in aerospace, automotive and aircraft industries due to their well known properties. Milling of GFRP composite materials is very difficult due to its heterogeneity and the number of troubles like as surface delamination during machining affects uniqueness of the material and the machining parameters. Present paper focuses the experimental details to find out delamination factor on GFRP composite laminates by using Taguchi's DOE L9 orthogonal array. The main objective of the present work is to optimize the process parameters in the drilling of GFRP composite using Taguchi DOE and to find the significance of each process parameter using ANOVA. As far as the effect of input factors are considered, the factors drilled material and spindle speed both have nearly predominant influence on the delamination factor of drilled holes on GFRP composite by using CNC milling process.