Slot milling is one of the most common mechanical operations for machining composite materials. Experiments were carried out in order to investigate the milling force and surface roughness during GFRP milling. An orthogonal exam was designed to explore the influence of machining parameters (spindle speed

feed rate and depth of cut) on milling force. Matlab is used to analyze the experimental data of milling force and surface roughness. After regression analysis

the milling force and surface roughness regression equations are established. Finally

the correctness of the milling force and surface roughness regression equations is verified by experiments. The results show that depth of cutting has a greatest influence on milling force

while the influence of feed rate is small; spindle speed has a greatest influence on surface roughness

while the influence of depth of cutting is small. And the error range of the milling force and surface roughness is within 20%.