The invention relates to a rear ball valve device for natural gas hydrate pressure coring. The rear ball valve device for natural gas hydrate pressure coring is characterized by comprising a ball valve lower part, a circular seal, a ball valve, and a ball valve upper part; the circular seal is disposed in the ball valve lower part, the ball valve is supported above the seal, and the ball valve upper part is supported on the ball valve and fitted in the ball valve lower part; the outer wall of one side of the ball valve lower part is axially provided with a through rack mounting hole, and the outer wall on the same side of the ball valve lower part is radially provided with a gear mounting hole; a gear is radially mounted in the gear mounting hole is a freely rotatable manner and is fixedly connected to a cavity of the outer wall of the ball valve through a jaw on the inner side of the gear; a rack is axially mounted in the rack mounting hole and meshed with the gear, and the rack is fixed on the ball valve lower part through hydraulic transmission pipes at two ends of the rack. By allowing a high-pressure pipe and the hydraulic transmission pipes to apply pressure of a hydraulic system upon the ends of the rack, allowing the rack to drive the gear to radially rotate and also allowing the gear to drive the ball valve to radially rotate, the ball valve can be closed to allow for natural gas hydrate pressure coring.