A piston pump, comprising a cylinder body, a piston, a main shaft, end covers, and an oil dispensing mechanism; wherein the cylinder body is coaxially connected to the main shaft; the piston is mounted in a cylinder bore of the cylinder body, and is configured to move along the cylinder bore; both ends of the cylinder body are sealed by the end covers; the oil dispensing mechanism comprises an oil suction mechanism and an oil discharging mechanism; a roller is mounted on the piston, and the roller is rotatablely connected to the piston; a driving wheel is arranged on the main shaft;; and a driving groove is formed on the driving wheel, and a roller-path surface of the driving groove is a curved surface; a size of the driving groove is adapted to an outer diameter of the roller; the main shaft rotates to drive the driving wheel to rotate to further drive the piston to move along the cylinder bore, and wherein a direction of the cylinder bore is perpendicular to a direction of a center line of the cylinder body; the piston is configured to move radially along the cylinder body; the driving wheel is mounted symmetrically on both sides of the cylinder body, and the driving wheel is classified into a left driving wheel and a right driving wheel according to an installation position; the driving groove of the driving wheel includes an inner roller-path surface and an outer roller-path surface; the inner roller-path surface and the outer roller-path surface are continuous surfaces; each of the continuous surfaces is smoothly connected end-to-end and is provided with a periodic undulation formed by convex portions and concave portions, wherein the convex portions and the concave portions are uniformly circumferentially distributed at intervals; the inner roller-path surface and the outer roller-path surface are concentrically nested together at an equal spacing, and a size of the spacing is adapted to the outer diameter of the roller; the roller is left-to-right symmetrically arranged on both sides of the piston, and the roller is correspondingly separately fitted in the driving groove of each of the left driving wheel and the right driving wheel; the roller is clamped between the inner roller-path surface and the outer roller-path surface to roll along the driving groove; a housing is mounted outside the cylinder body, and the housing is provided with an oil discharging opening; the main shaft is supported on the housing, the end cover or the cylinder body through a bearing, wherein the driving wheel is mounted in cooperation with the main shaft, or the driving wheel is integrally formed with the main shaft. the cylinder body is coaxially connected to the main shaft; the piston is mounted in a cylinder bore of the cylinder body, and is configured to move along the cylinder bore; both ends of the cylinder body are sealed by the end covers; the oil dispensing mechanism comprises an oil suction mechanism and an oil discharging mechanism; a roller is mounted on the piston, and the roller is rotatablely connected to the piston; a driving wheel is arranged on the main shaft;; and a driving groove is formed on the driving wheel, and a roller-path surface of the driving groove is a curved surface; a size of the driving groove is adapted to an outer diameter of the roller; the main shaft rotates to drive the driving wheel to rotate to further drive the piston to move along the cylinder bore, and wherein a direction of the cylinder bore is perpendicular to a direction of a center line of the cylinder body; the piston is configured to move radially along the cylinder body; the driving wheel is mounted symmetrically on both sides of the cylinder body, and the driving wheel is classified into a left driving wheel and a right driving wheel according to an installation position; the driving groove of the driving wheel includes an inner roller-path surface and an outer roller-path surface; the inner roller-path surface and the outer roller-path surface are continuous surfaces; each of the continuous surfaces is smoothly connected end-to-end and is provided with a periodic undulation formed by convex portions and concave portions, wherein the convex portions and the concave portions are uniformly circumferentially distributed at intervals; the inner roller-path surface and the outer roller-path surface are concentrically nested together at an equal spacing, and a size of the spacing is adapted to the outer diameter of the roller; the roller is left-to-right symmetrically arranged on both sides of the piston, and the roller is correspondingly separately fitted in the driving groove of each of the left driving wheel and the right driving wheel; the roller is clamped between the inner roller-path surface and the outer roller-path surface to roll along the driving groove; a housing is mounted outside the cylinder body, and the housing is provided with an oil discharging opening; the main shaft is supported on the housing, the end cover or the cylinder body through a bearing, wherein the driving wheel is mounted in cooperation with the main shaft, or the driving wheel is integrally formed with the main shaft.