The invention discloses a clamping mechanism of a planetary gear system. The clamping mechanism comprises a motor, a chassis, a positioning slide block, a gear shaft, the planetary gear system, a rotary disc, a central screw, a connecting rod, a material disc and a clamping guide rod from top to bottom in sequence, wherein the planetary gear system is formed by surrounding a drive gear through a plurality of driven planetary gears; the motor is fixedly connected with the drive gear of the planetary gear system through the chassis; the planetary gear system is arranged on the rotary disc; the first end of the gear shaft is connected with the positioning slide block; the second end of the gear shaft is connected with the driven planetary gears of the planetary gear system, and is fixedly connected with the connecting rod through the rotary disc; the first end of the gear shaft is connected with the positioning slide block; the second end of the gear shaft is connected with the driven planetary gears of the planetary gear system and is fixedly connected with the connecting rod through the rotary disc; the central screw is used for connecting the rotary disc to the material disc; and the clamping guide rod is fixedly connected with the connecting rod through the material disc. The clamping mechanism of the planetary gear system is compact in structure, is simple to mount, is simpleto maintain, and reduces the cost.