The invention discloses a 3D model nesting and placing method based on model similarity. The method comprises the following steps that 1, carrying out voxelization on the surface of a 3D model; 2, combining and classifying the voxelized 3D model according to the similarity, and dividing the 3D model into similar model group and non-similar model; 3, nesting and placing the similar model group and the non-similar model group according to a yzx axis sequence to obtain a placing area; and 4, in the placing area, carrying out iterative nested placement on the similar model group and the non-similar model according to a yxz axis sequence, and updating the area after each iteration till that the iteration is completed. The method comprises the following steps: firstly, according to a voxelized 3D model, performing similarity classification combination on the 3D model, then performing nested placement in the yzx direction to obtain a placing area, finally performing nested placement in the yxz direction, and iteratively adjusting the size in the xy direction to minimize the placing area each time. And through similarity combination, supporting materials between the models are reduced, and the models are easy to take down after printing is completed.