A pump body assembly, comprising: an upper flange; a lower flange; a cylinder, arranged between the upper flange and the lower flange; a sliding block structure, rotatably arranged inside the cylinder, the sliding block structure comprising a connecting portion and two sliding sub-blocks arranged on the connecting portion, and the two sliding sub-blocks and an inner wall surface of the cylinder forming a first sliding hole; a piston, slidably arranged inside the first sliding hole, a variable volume cavity being formed between the piston and an inner wall of the cylinder, and the piston having a second sliding hole; and a rotation shaft, wherein at least a portion of the rotation shaft is slidably arranged inside the second sliding hole, and a slide included angle is formed between a first sliding direction, in which the piston slides relative to the first sliding hole, and a second sliding direction, in which the rotation shaft slides relative to the second sliding hole; at least one connecting portion, wherein the at least one connecting portion is provided with a first through hole and the rotation shaft passes through the first through hole; a first connecting portion is arranged on the connecting portion; a second connecting portion is arranged on the lower flange; and the first connecting portion and the second connecting portion are nested and fit to connect the sliding block structure with the lower flange; characterized in that the first connecting portion is the first through hole; the second connecting portion is a position-limiting protrusion; the position-limiting protrusion extends into the first through hole to enable the sliding block structure to pivot relative to the lower flange; the position-limiting protrusion has a second through hole; and the rotation shaft passes through the second through hole. an upper flange; a lower flange; a cylinder, arranged between the upper flange and the lower flange; a sliding block structure, rotatably arranged inside the cylinder, the sliding block structure comprising a connecting portion and two sliding sub-blocks arranged on the connecting portion, and the two sliding sub-blocks and an inner wall surface of the cylinder forming a first sliding hole; a piston, slidably arranged inside the first sliding hole, a variable volume cavity being formed between the piston and an inner wall of the cylinder, and the piston having a second sliding hole; and a rotation shaft, wherein at least a portion of the rotation shaft is slidably arranged inside the second sliding hole, and a slide included angle is formed between a first sliding direction, in which the piston slides relative to the first sliding hole, and a second sliding direction, in which the rotation shaft slides relative to the second sliding hole; at least one connecting portion, wherein the at least one connecting portion is provided with a first through hole and the rotation shaft passes through the first through hole; a first connecting portion is arranged on the connecting portion; a second connecting portion is arranged on the lower flange; and the first connecting portion and the second connecting portion are nested and fit to connect the sliding block structure with the lower flange; characterized in that the first connecting portion is the first through hole; the second connecting portion is a position-limiting protrusion; the position-limiting protrusion extends into the first through hole to enable the sliding block structure to pivot relative to the lower flange; the position-limiting protrusion has a second through hole; and the rotation shaft passes through the second through hole.