The invention provides an injector, a rocket engine and a rocket, and relates to the technical field of vehicles. The injector comprises an upper bottom, a middle bottom and a lower bottom, wherein one side of the middle bottom is connected with the upper bottom, a gas collecting cavity and a gas channel are arranged between the middle bottom and the upper bottom, the gas channel communicate the gas collecting cavity with a combustion chamber, and the gas collecting cavity is provided with a gas inlet; the other side of the middle bottom is connected with the lower bottom, a liquid collectingcavity is formed between the middle bottom and the lower bottom, and the liquid collecting cavity is provided with a liquid inlet; and the injector further comprises a pin bolt which penetrates through the lower bottom, the liquid collecting cavity and the middle bottom, the pin bolt is in sealing connection with the lower bottom, and a liquid channel used for communicating the liquid collecting cavity with the combustion chamber is arranged between the pin bolt and the middle bottom. In the injector, a gas propellant can enter the gas collecting cavity through the gas inlet and then enters the combustion chamber through the gas channel, and the liquid propellant can enter the liquid collection cavity through the liquid inlet and then enters the combustion chamber through the liquid channel, that is to say, the injector is capable of achieving a jet of a two-component propellant of a gas and a liquid.