The present disclosure provides a 3D printing method including: a resin providing step of providing a dual cure resin; a light curing step of irradiating the dual cure resin by an ultraviolet light to perform 3D printing so as to form an intermediate body having a predetermined lattice shape; a stretching step of applying a stress on the intermediate body in a stretching direction according to a stretching ratio of a predetermined size to stretch and form a stretched body; and a thermal curing step of heating the stretched body to perform thermal curing and shaping so as to form a 3D printing formed body. When the light curing step is performed, a size in a non-stretching direction of the intermediate body is correspondingly pre-compensated based on the stretching ratio. The present disclosure further provides a 3D printing formed body.