convenient maintenance application_number US 201214389651 A description referring to fig1 and fig2 a permanent magnet linear piston pump 3 of the present invention comprises a piston body 1 a cylinder body 2 a permanent magnet assembly 6 and an electromagnetic coil 3 the cylinder body is in a shape of a polygonal prism such as in a prism with four to six sides preferably a quadrangular prism is adopted as shown in fig4 this preferred embodiment has a quadrangular cylinder body 2 whose cross section is shaped by a rectangular contour an interior of the cylinder 2 arranges a piston cavity 201 formed by an axial columnar accommodating cavity the piston body 1 is arranged in the piston cavity 201 by a liquid sealing movable fit mode a cross section of one end of the piston body 1 can be the same as the cross section of the piston cavity 201 this end is inserted into the piston cavity 201 by the liquid sealing movable fit mode in this preferred embodiment as shown in fig2 and fig3 the piston body 1 is a prism whose cross section is the same as the cross section of the piston cavity 201 the end.