The utility model discloses a double-C-shaped aluminium-wood-plastic composite building template support keel which comprises a metal wrapping frame and a filling material, wherein the metal wrapping frame consists of two C-shaped high-strength light-weight aluminium alloy sections with opening directions which are reversely arranged; two webs are fixedly connected into a whole; the filling material which is adaptive to the shape of the metal wrapping frame fills the cavity of the metal wrapping frame; the filling material is a wood-plastic composite foaming material; the filling material wholly penetrates through or is arranged in the cavity of the metal wrapping frame by sections at intervals. The double-C-shaped aluminium-wood-plastic composite building template support keel has the advantages that the mass is light, the operation is convenient, the construction efficiency is favorably improved, and the labor and material resources are saved in the building construction process; the holding force to nails is increased by a wood-plastic composite foaming core material, and the fixation of a building template is facilitated; the aluminium alloy sections are adopted as the wrapping frame, the strength of the keel is increased and the core material is protected; the keel is adjustable in length, and the installation is flexible; the core material is a recovered material, and the keel is a green and environment-friendly material-saving support keel with wide market prospects.