The lightweight of light-curing 3D printed resin dental cast was studied based on the code of design for additive manufacturing (DfAM), aiming at reducing the cost of manufacturing invisible orthodontic appliances without brackets. By using macroscopic topology optimization and matrix filling, 7 kinds of dental casts were established. Through ANSYS finite element simulation, 3 kinds of optimal dental casts were selected to conduct 3D deviation experiment, and their physical and mechanical properties under pressure were evaluated. The results show that under the premise of ensuring the manufacturing accuracy of the invisible orthodontic appliance, the mass reduction ratio of the two-dimensional honeycomb lattice filling dental cast reaches 21.67% compared with the initial dental cast, indicating that it is the best lightweight design scheme.