The tooth modification is an effective way to improve the contact fatigue life of gear contacts.A new flank modification, tangential parabola, was proposed and applied to cylindrical spur gear transmission.The contact fatigue experiments were carried out on a standard FZG test rig to examine the fatigue life of gear teeth with and without flank modification, and under different working conditions of the gear.The experimental results show that this flank modification can significantly improve the contact fatigue life of gear teeth, and clean lubricants can improve the fatigue life inthreefold ascompared with that of the dirt lubricant.The lubricants with extreme pressure additives can remarkably improve the contact fatigue life, and preventearly happening of the scuffing failure of gear teeth surfaces.