The invention belongs to the field of downhole tools for oil extraction in an oil field, and particularly relates to a self-expanding type automatic oil drainage device. The self-expanding type automatic oil drainage device comprises an upper joint, a center pipe, a lower joint, an outer center pipe, shear nails, an upper jacket, an elastic damping ring assembly, a clamping spring carrier, a clamping spring and a lower jacket; the upper end of the center pipe is in threaded connection with the upper joint; oil drainage holes are formed in the side wall of the center pipe below the threaded connection part and the side wall of the upper joint corresponding to the threaded connection part; the outer center pipe sleeves the center pipe; an annular cavity for liquid passing is reserved betweenthe outer center pipe and the center pipe, and is called a liquid passing channel; the upper end of the outer center pipe sleeves the upper joint and blocks the oil drainage holes; the outer center pipe is connected with the upper joint through the shear nails; the upper outer sleeve sleeves the outer center pipe; and an annular cavity is reserved between the upper outer sleeve and the outer center pipe. Complicated procedures such as pressing, repeatedly lifting and releasing a pipe column, throwing a heavy object and the like required by the conventional oil drainage device are solved; andthe self-expanding type automatic oil drainage device can achieve the effect of automatic oil drainage along with the linkage of the pipe column, so that the operation efficiency is greatly improved.