Friction and wear behavior of nitrile rubber in crude oil medium with different size and shaped sand (sharp and round)was investigated by the reciprocating wear tester,and morphology and element content of worn surface were measured by stereo microscope and field emission scanning electron microscope.The results show that,with the increasing of sand size,the friction coefficient and wear loss of rubber in crude oil medium are gradually increased,while with the increasing of load,the friction coefficient is decreased,and the wear loss is increased.The presence of sharp sand leads greater friction coefficient and wear loss than round sand under the same load and sand size.In the case of small load,the movement of different sand size is mainly rolled,while in the case of large load,the movement of sand on material surface begin to slide when the size of sharp sand increases to 1 mm.The destruction of molecular chain becomes severe with the increasing of sand size and load,which leads C element percentage content on worn surface to reduce.