An electronic parking brake actuator comprising: a gearbox body provided with a motor accommodation cavity and a gear train accommodation cavity; the gear train accommodation cavity being provided with an inner gear ring inside, and the gearbox body being provided with an output spline hole at a position corresponding to a center of the inner gear ring; a gearbox cover configured for covering the gearbox body and sealing the gear train accommodation cavity; a motor arranged in the motor accommodation cavity, an output shaft of the motor extending into the gear train accommodation cavity and being fixed with a first gear; a primary transmission gear assembly rotatably fitted in the gear train accommodation cavity, the primary transmission gear assembly comprising a second gear and a third gear that are coaxially arranged and rotate synchronously, wherein the second gear is engaged with the first gear; a secondary transmission gear assembly rotatably fitted in the gear train accommodation cavity, the secondary transmission gear assembly comprising a fourth gear and a sun gear that are coaxially arranged and rotate synchronously, wherein the fourth gear is engaged with the third gear; a planetary gear transmission assembly comprising a planetary gear carrier, a plurality of planetary gears and an output spline, the plurality of planetary gears being rotatably mounted on a first end surface of the planetary gear carrier in an axial direction, the output spline being fixedly fitted on a second end surface of the planetary gear carrier in the axial direction, all of the plurality of planetary gears being engaged with the sun gear and the inner ring gear, the output spline extending out of the gearbox body from the output spline hole; characterized in that: the primary transmission gear assembly is sleeved on a primary gear positioning pin, a lower end of the primary gear positioning pin is pressed into the gearbox body in an online press-fitting manner; the secondary transmission gear assembly is mounted on the gearbox cover through a secondary gear positioning pin, wherein an upper end of the secondary gear positioning pin is mounted on the gearbox cover, and a lower end of the secondary gear positioning pin is press-fitted on the sun gear; the sun gear is manufactured by powder metallurgy, and the fourth gear is injection-molded with a middle part between the sun gear and the secondary gear positioning pin as an insert. a gearbox body provided with a motor accommodation cavity and a gear train accommodation cavity; the gear train accommodation cavity being provided with an inner gear ring inside, and the gearbox body being provided with an output spline hole at a position corresponding to a center of the inner gear ring; a gearbox cover configured for covering the gearbox body and sealing the gear train accommodation cavity; a motor arranged in the motor accommodation cavity, an output shaft of the motor extending into the gear train accommodation cavity and being fixed with a first gear; a primary transmission gear assembly rotatably fitted in the gear train accommodation cavity, the primary transmission gear assembly comprising a second gear and a third gear that are coaxially arranged and rotate synchronously, wherein the second gear is engaged with the first gear; a secondary transmission gear assembly rotatably fitted in the gear train accommodation cavity, the secondary transmission gear assembly comprising a fourth gear and a sun gear that are coaxially arranged and rotate synchronously, wherein the fourth gear is engaged with the third gear; a planetary gear transmission assembly comprising a planetary gear carrier, a plurality of planetary gears and an output spline, the plurality of planetary gears being rotatably mounted on a first end surface of the planetary gear carrier in an axial direction, the output spline being fixedly fitted on a second end surface of the planetary gear carrier in the axial direction, all of the plurality of planetary gears being engaged with the sun gear and the inner ring gear, the output spline extending out of the gearbox body from the output spline hole; characterized in that: the primary transmission gear assembly is sleeved on a primary gear positioning pin, a lower end of the primary gear positioning pin is pressed into the gearbox body in an online press-fitting manner; the secondary transmission gear assembly is mounted on the gearbox cover through a secondary gear positioning pin, wherein an upper end of the secondary gear positioning pin is mounted on the gearbox cover, and a lower end of the secondary gear positioning pin is press-fitted on the sun gear; the sun gear is manufactured by powder metallurgy, and the fourth gear is injection-molded with a middle part between the sun gear and the secondary gear positioning pin as an insert.