The invention provides a 3D printing auxetic yarn, a processing method and an application. The 3D printing auxetic yarn is characterized by comprising a multi-layer structure formed by 3D printing, the surface of each layer comprises aN auxetic geometric structure, and the adjacent layers are connected to each other. The 3D printing auxetic yarn, the processing method and the application can be applied to the design of the auxetic yarns with simple structures, and with complex structures such as non-cylindrical section auxetic yarns, composite yarns and the like, and the obtained stretched yarn structures has good controllability; and meanwhile, the system is simple in implementation process, a large number of intermediate processes are not needed, damage to the yarn performance due to themulti-stage process in the traditional spinning process is avoided, yarns with the optimal performance under the design structure can be obtained, the production efficiency is high, the manufacturedyarn is good in tensile effect and stable in structure, the mechanical property is excellent, adjustability is large, and the basic requirements of functional textiles can be met.