The invention provides a 3D printer for glass products in complicated shapes and a preparation method. A carbon dioxide laser focuses on a discrete material obtained by glass 3D printing to melt the discrete material, then annealing and cooling are performed to form glass, and shaping is carried out while a substrate moves to control a shaping area. The glass 3D printing material is continuously provided through a powder feeding device or a filament feeding device to guarantee continuity of 3D printing, and a 'dot-line-plane-solid' additive manufacturing process is realized. 3D printing of theglass products in the complicated shapes is realized.