Cooling/lubrication conditions have significant influences on surface integrity, chip morphology, tool life and eventually productive efficiency when machining titanium alloy Ti6Al4V. Milling experiment under different cooling/lubrication conditions, namely dry, wet, MQL and nitrogen gas jet were conducted. Cutting forces, surface roughness and chip morphology are obtained. It is shown that cooling/lubrication conditions influence cutting force greatly while its effect on surface roughness is not obvious. The chip surface contacted with rake face under nitrogen gas is smoother than that under dry, but there exists nitrogen adsorption of the chip at higher speed.