The invention discloses a bottom valve of a reaction kettle. The bottom valve comprises a valve body with an inner cavity, wherein a feed opening is formed in the top of the valve body, and a discharge hole is formed in the side wall of the valve body; a static sealing body is arranged at the upper end of the valve body; first feeding holes penetrating the static sealing body up and down are formed in the static sealing body; a valve rod upwardly penetrates the valve body and the static sealing body to be connected with a locknut; a movable sealing body is arranged between the locknut and the static sealing body; second feeding holes penetrating the movable sealing body up and down are formed in the movable sealing body; the lower end of the valve rod is connected with a rotary handle; a spring tray is arranged between the rotary handle and the valve body; springs are arranged between the spring tray and the valve body and enable the movable sealing body to always downwardly compress and fit the static sealing body in a sealing manner; and when the movable sealing body rotates till the second feeding holes and the first feeding holes communicate with each other, the first feeding holes and the second feeding holes form a feeding channel, and when the movable sealing body rotates till the second feeding holes are staggered with the first feeding holes, the feeding channel is cut off. The bottom valve has the advantage that the influence of a discharge pup joint on reaction precision in the reaction kettle can be completely eliminated.