Abstract: NiTi alloys have attracted much attention due to their unique shape memory properties and superelasticity, and gradient grain has wide application prospects as a method to improve the strength and ductility of materials. In this study, gradient finite element models are constructed based on the grain distribution function, which takes into account the crystal plasticity theory model and cohesive element. The uniaxial and compact tensile fracture processes of homogeneous and gradient polycrystalline NiTi are simulated, and the influence of different structure polycrystals on the strength and ductility of the material is discussed. The macro - micro mechanical laws are analyzed. The conclusions are as follows: The smaller the grain size, the stronger the polycrystal resistance to crack initiation, the larger the grain size, the stronger the polycrystal resistance to crack propagation. The fracture behavior of NiTi polycrystalline has significant orientation correlation, and the 110 texture has the best fracture resistance. Gradient polycrystals can play a coordinating role between the strength and ductility of NiTi alloy materials. The fine crystal structure is distributed at both ends of the polycrystal to withstand higher stress and resist the generation of cracks, while the coarse-crystal structure is distributed in the middle of the polycrystal to provide a zigzagging grain boundary shape and hinder the propagation of cracks.