Wear characteristics were influenced by the parameters of wear-testing apparatus including configuration of contact surface and form of the relative motion. The tribological behavior of polytetrafluoroethylene (PTFE) disk against AISI1045 steel pin under unidirectionally rotating, linearly reciprocating, and torsional motion was studied. The friction coefficients under unidirectional rotating, linearly reciprocating and torsional motion were 0.1, 0.118 and 0.12, respectively. The highest wear mass loss of PTFE was obtained under linearly reciprocating. The wear mass loss under torsional motion was lowest. The wear mechanism of PTFE under unidirectional rotating, linearly reciprocating, and torsional motion was slight plowing, serious abrasive wear, and adhesive wear, respectively. Through finite element analysis, a higher normal stress induced by the edge effect of steel pin promoted a higher shear stress in PTFE disk. The plastic ratcheting mechanism occurred on the contact edge when the steel pin entered and exited the contact zone, as led to higher wear mass loss under linearly reciprocating and unidirectional rotation. The plastic ratcheting mechanism did not occur under torsional motion. Different transfer films with various topographies were formed on the steel pins under the three motions.