The invention discloses a runner converting device of a gas-injection well. The runner converting device comprises an upper connecting body and a lower connecting body which are in sealing connection through an oil tube fastener, wherein the lower connecting body comprises a first shaft section with the minimal diameter, a second shaft section which is in sealing connection with the upper connecting body and a third shaft section with the maximal diameter; the side wall of the first shaft section is provided with a side hole; a ring-shaped cavity is formed between the first shaft section and the upper connecting body; at least one radial hole is formed in the third shaft section; a central hole which communicates with the radial hole is formed from the first shaft section and the second shaft section to part of the third shaft section; the position of the side hole of the first shaft section is hinged with a sealing mechanism capable of sealing the side hole or the central hole; an eccentric hole which is isolated from the central hole and communicates with the ring-shaped cavity is formed from the second shaft section to the third shaft section; and an inner core tube is arranged inside the upper connecting body. The runner converting device of the gas-injection well provided by the invention can simply and conveniently change a gas injection runner of the gas-injection well, and is used for realizing multi-layer gas injection of a multi-layer oil deposit gas-injection well.