In order to improve the fracture toughness of C60 concrete, the influence law of polyacrylonitrile fiber on the mechanical properties of C60 concrete was investigated. On the basis of 7d, 28d compressive strength and split tensile strength, the three-point bending fracture performance test was carried out by digital image correlation method. The influence laws of different polyacrylonitrile fiber admixtures (0.6kg/m3, 0.9kg/m3, 1.2kg/m3, the same below) on the starting fracture toughness and the destabilized fracture toughness of C60 concrete were analyzed based on the double-K fracture theory. In addition, an energy-based linear softening damage model based on the extended finite element method was established by Abaqus software to simulate the three-point bending fracture of concrete beams and the crack damage evolution process. The results show that: three kinds of polyacrylonitrile fiber dosage on C60 concrete splitting tensile strength have a significant trend of improvement, the enhancement of the magnitude of 33.36%, 37.90%, 25.28%, respectively, and the impact on compressive strength is not significant, in the dosage of small compressive strength has a small increase; based on the double K fracture theory, three kinds of fiber dosage on the starting cracking toughness enhancement of 24.23%, 70.59% and 70.59%, respectively. 24.23%, 70.59%, 25.96%, and the enhancement of destabilized fracture toughness was 5.81%, 55.93%, 13.59%, respectively, and the optimum dosage of polyacrylonitrile fibers was determined to be 0.9kg/m3; polyacrylonitrile fibers gradually assumed the loading during the cracking process of the concrete matrix, which altered the crack morphology and the trend of the cracks, and caused the cracks to develop from the main cracks to a number of The load-crack opening displacement curves obtained by extended finite element numerical simulation are in good agreement with the test results, which can better characterize the fracture process and crack evolution trend of polyacrylonitrile fiber concrete. The research results provide reference and basis for the theory, method and engineering application of high-performance concrete reinforcement and toughening.