Arrow type drain valve for casing pipe of drilling platform

The invention discloses an arrow type drain valve for a casing pipe of a drilling platform. The arrow type drain valve is used for draining liquid and depressurizing inside the casing pipe and comprises a cylindrical valve body, a valve cavity, a runner, an arrow-shaped plug , lugs, a lifting hook and cups, wherein the valve cavity is arranged on the upper side of the inside of the valve body, the runner longitudinally runs through the upper side and the lower side of the valve body and the valve cavity, the arrow-shaped plug is arranged in the valve cavity and partially extends into the runner, the lugs are arranged on the top of the valve body, ends of the hood are connected with the lugs, and the cups are circularly arranged in the middle of the valve body. The arrow-shaped plug is provided with a handle portion and a tip portion, and a reset spring sleeves the handle portion so that the tip portion can extend into the runner to plug a runner opening of the bottom of the valve cavity. The drain valve for the casing pipe can sink to the position slightly above a pre-cut position along the inside of the casing pipe, the runner is closed and sealed by the arrow-shaped plug, the cups cling to the inner wall of the casing pipe, liquid in the casing pipe is separated into two parts, by this time, jetting can be avoided in the process of cutting the casing pipe, the casing pipe can be quickly cut and cutting efficiency is greatly improved.