The invention discloses a socket-welding modular aluminium alloy-wood composite template system and a mounting method thereof. The composite template system is composed of composite templates and a fixing device. The composite templates are composed of multiple aluminium alloy keels and multiple wood templates, the aluminium alloy keels and the wood templates are connected through socket welding,and multiple layers of composite templates are vertically connected; the fixing device comprises longitudinal dorsal bars and transverse dorsal bars. Accordingly, the advantages of a traditional woodtemplate and an aluminum alloy template can be combined, rapid mounting can be achieved, and the good economical efficiency is achieved.