The shape of clothing accessories includes internal styling and external styling. Through analyzing roles that 3D printing plays in spatial relations construction of garment accessories and in realizing these roles through utilizing internal processes and materials, 3D printing's functions in constructing the internal styling of garment accessories are highlighted; through analyzing its applications in functional additions and styling of garment accessories, 3D printing's applications in external styling of garment accessories are also reflected. Based on the manufacturing principle and material properties of 3D printing technology, this paper takes the castle backpack design as the experimental object, carries out experimental analysis and research. In the course of the experiment, 3D printing technology solved the difficulty of the castle modeling, the work is fine and the success rate is higher. The advantages of these experiments can be seen in every design and manufacture. The maturity of 3D printing technology makes the complex and changeable garment accessories design can be obtained by 3D printing technology. The success of the experiment provides a 3D printing technology information library for the design of clothing accessories.