A toy gun magazine constant gas flow valve structure is coupled with a magazine of a pneumatic toy gun and structurally includes a gas valve body fixed in the magazine and includes a gas inlet end portion, a gas discharge portion, and a coupling end portion, a driving rod movably disposed in the gas valve body, a control member coupled with one end of the driving rod, a stroke limiting trough having a front limiting portion and a rear limiting portion, and a stop element. Before the toy gun is firing, the stop element abuts the front limiting portion to control the extent by which the driving rod presses against the leak-sealing element and after the firing of the toy gun, the stop element abuts the rear limiting portion to control the extent of opening of the gas inlet end portion and the gas discharge portion.