The present invention discloses a missile ejection system and a canister thereof. The missile ejection system comprises: comprising: a canister formed as a cylindrical shell, a partition wall protruding from an inner wall of the canister so as to divide the canister into a first chamber for housing a missile therewithin and a second chamber, and having at least one hole therethrough for allowing the flowing of gas through the partition wall, a gas generator secured to the partition wall in the second chamber so that a gas outlet thereof faces in an opposite direction from the first chamber, and an obturator including a sealing plate formed with a concave surface toward a fore-end of the missile for enclosing a tail end of the missile, and a radially extending skirt plate extended from the circumference of the sealing plate to the inner wall of the canister and inclined toward the fore-end of the missile for covering the space between the missile and the inner canister, wherein the missile is propelled by the pressure of the gas discharged out of the gas generator from the second chamber to the first chamber through the hole, being pressurized by the flown-in gas in the first chamber, pushing upon the obturator. Thereby, the system is able to effectively release a missile from a canister by a gas generator without using a missile propulsion engine, thereby fundamentally preventing the damage of ground equipments or peripheral missiles.