This paper introduces the manufacturing method of the middle fuselage plenum of the light business jet. The middle fuselage is a semi-closed cabin. Considering the detachable mold of the formed parts, and the ease of processing and forming, the tooling cannot be made into a whole. It is manufactured by using the upper and lower parts to solve the problem of insufficient space for parts. After the upper and lower molds are respectively laid and finished, the mold is formed by a co-solidification molding method. In this way, the bearing capacity requirements of the fuselage can be achieved, and the structural weight reduction can be achieved by 30%, and the foundation for the civil airworthiness road of the domestic main bearing composite component is laid. Compared with the original non-integrated fuselage structure, the fuselage of the composite material is co-cured, no fastener connection, no secondary bonding, reducing the number of tooling more than 100, simplifying the entire process of molding.