A plunger pump includes a plunger pump tappet assembly and a roller. The roller includes a revolving body configured to revolve along a central axis. The revolving body includes logarithmic parts and a straight part which are integrally formed. The logarithmic parts are symmetrically provided at two ends of the straight part in an axial direction of the central axis. In a cross section of the revolving body along and through the central axis, an outline of the straight part forms a straight line, and an outline of the logarithmic part forms a logarithmic curve, with an X-axis lying along the central axis, and a perpendicular bisector of the X-axis as a Y-axis.