Abstract: A new two-layer brake block for oil rig was designed. The effect of nitrile butadience rubber(NBR) on mechanical and tribological performances of friction materials was studied. The material formula of friction layer of brake blocks was optimized with uniform design method and SAS software. The results show that the NBR could significantly increase impact strength of the friction material, and reduce the hardness and density; the coefficient of friction of the material with optimized formula was high and stable, the rate of wear was low. Compared with merchant semi-metal brake blocks, the rate of heat and wear fade and wear might decrease by about 51% and 34.7% at 350 ℃. The developed two-layer brake block braked sensitively and noiselessly, its working life prolonged over 60%.