Abstract: The size control equation of the thermal expansion mould was derived from the relative relation between the expansion pressure of the thermal expansion mould and the wall thickness of the composite thrust cylinder and the thickness of the preform used for fabricating the composite thrust cylinder. The thermal expansion mould was fabricated by an integrally casting method. The axial compressive experiment on the integrally fabricated thrust cylinder shows that the thrust cylinder has good mechanical properties and satisfies the design specification. Compared with traditional VARTM, the thermal expansion mould assisted RTM process improves the fiber volume fraction by squeezing the resin out through an inflated thermal expansion mould and improves the compactness of the composites by expansion pressure of the mould; therefore the mechanical properties of the composites were increased.