The invention provides a microwave-based heat conversion tube, a manufacturing method and a thermal propulsion system, and belongs to the technical field of energy conversion. The microwave-based heatconversion tube comprises a microwave absorbing tube and a supporting tube nested in the microwave absorbing tube, wherein the microwave absorbing tube is used for absorbing microwaves, and the innerdiameter of the microwave absorbing tube is 1-10 mm, the wall thickness is an integer multiple of a quarter of the microwave wavelength, and the supporting tube is used for bearing the expansion pressure of liquid gas. According to the microwave-based heat conversion tube, the manufacturing method and the thermal propulsion system, the heat conversion tube is used for heating the liquid gas, thehigh-temperature liquid gas is sprayed out so that the propulsion force with the KN magnitude can be generated, a traditional chemical propulsion mode can be replaced, and the increase of the weight of an aircraft due to the fact that the fuel and an oxidizing agent are carried is avoided.