When nitrile rubber (NBR) contacts with water medium during the service life,the swelling and wear occurs.In order to study the influence of swelling aging on the sliding wear behavior of nitrile rubber,the swelling tests of different immersion time were conducted on three kinds of nitrile rubber samples with different acrylonitrile contents.To investigate the swelling effect on the twobody sliding wear behavior of nitrile rubber,unidirectional sliding wear tests were conducted on the nitrile rubber samples before and after swollen by MPV600 ringonblock wear tester in water lubrication conditions respectively.Scanning electron microscopy (SEM) analysis was performed to interpret the wear surface accordingly.The results show that,compared with the sliding wear of unswollen nitrile rubber sample,the friction coefficient of the swollen sample is decreased,while the wear loss is increased after swelling.The swelling effect performs obviously within 72 h and turns to be gradually stabilized after longer immersion.The swelling effect of the three kinds of nitrile rubbers is decreased with the increase of acrylonitrile content.After swelling,the decrease in the molecular chain elasticity and the appearance of the holedefects lead to the easier wear behavior of the samples.