In order to find the appropriate counter materials of friction pairs for water hydraulic pump/motor,the friction pairs composed of 316 L stainless steel and four kinds of polyetheretherketone(PEEK),including pure PEEK,30% glassfiberreinforced PEEK(PEEKGF30),30% carbonfiberreinforced PEEK(PEEKCA30),and PTFE,graphite and carbonfiberreinforced PEEK(PEEKHPV) were taken as study objects,the friction coefficient and temperature of the contact surface of the friction pairs,and their wear extent under water lubrication were measured by using a MMW1 vertical universal friction and wear tester.The worn surface morphologies of the samples were analyzed by a laser scanning confocal microscope.The results show that,among the four sets of friction pairs,the friction pairs of 316 LPEEKHPV has the lowest friction coefficient,friction temperature and wear extent,they are more suitable for the counter materials of key friction pairs in water hydraulic pump/motor.The friction mechanism is abrasion and scratch for the counter materials of 316 L stainless steel and PEEKGF30,which results in the serious wear.The friction mechanism is scratch for the counter materials of 316 L stainless steel and PEEKCA30,while the friction mechanism is mainly scuffing for the counter materials of 316 L stainless steel and PEEKHPV,and the wear of the friction pairs is slight