The present disclosure discloses a device capable of automatically replacing screen mechanism for light curing 3D printer, which comprises a resin tank and a worktable mounted on the resin tank and further comprises a screen mechanism, the screen mechanism comprises a screen exchanging assembly and a sliding assembly, the screen exchanging assembly is mounted on the sliding assembly and achieves exchanges of screens through the sliding assembly, the sliding assembly comprises at least one guide rail assembly in any angle, the screen exchanging assembly comprises at least two adjacently arranged movable screen devices, and the movable screen devices achieves front and back, left and right and any angle position exchange through the guide rail assembly. The present disclosure avoids a defect of time and labor consumption caused by manual replacement of the screens, reduces the labors and improves the production efficiency.