A computer-implemented method for optimizing global tritium breeding ratio of a tritium breeding blanket in a fusion reactor, comprising following steps: S1. performing three-dimension neutronics transport calculation based on an initial scheme of the tritium breeding blanket of the fusion reactor firstly, and performing first-order perturbation calculations and second-order perturbation calculations for each geometric boundary and each density of each function region secondly, so as to obtain local tritium breeding ratios in each energy group of each tritium breeding region in each perturbation state of the initial scheme; S2. calculating first-order perturbation coefficients and second-order perturbation coefficients in each energy group of each tritium breeding region of each perturbation state based on the local tritium breeding ratios in each energy group of each tritium breeding region in each perturbation state of the initial scheme; and constructing a multi-dimensional second-order analytic function based on the first-order perturbation coefficients and the second-order perturbation coefficients, wherein the multi-dimensional second-order analytic function illustrates the relationship of the global tritium breeding ratio and boundary disturbances and density disturbances of each function region; S3. performing an optimization for the global tritium breeding ratio based on the simulated annealing algorithm within an effective range of the perturbation calculations to find a global optimal blankets scheme according to the multi-dimensional second-order analytic function; S4. repeating steps S1 to S3 until convergence occurs, so as to obtain the global optimal blankets scheme of the tritium breeding blankets of the fusion reactor with the best tritium breeding performance; and implementing the global optimal blankets scheme in the tritium breeding blankets of the fusion reactor. S1. performing three-dimension neutronics transport calculation based on an initial scheme of the tritium breeding blanket of the fusion reactor firstly, and performing first-order perturbation calculations and second-order perturbation calculations for each geometric boundary and each density of each function region secondly, so as to obtain local tritium breeding ratios in each energy group of each tritium breeding region in each perturbation state of the initial scheme; S2. calculating first-order perturbation coefficients and second-order perturbation coefficients in each energy group of each tritium breeding region of each perturbation state based on the local tritium breeding ratios in each energy group of each tritium breeding region in each perturbation state of the initial scheme; and constructing a multi-dimensional second-order analytic function based on the first-order perturbation coefficients and the second-order perturbation coefficients, wherein the multi-dimensional second-order analytic function illustrates the relationship of the global tritium breeding ratio and boundary disturbances and density disturbances of each function region; S3. performing an optimization for the global tritium breeding ratio based on the simulated annealing algorithm within an effective range of the perturbation calculations to find a global optimal blankets scheme according to the multi-dimensional second-order analytic function; S4. repeating steps S1 to S3 until convergence occurs, so as to obtain the global optimal blankets scheme of the tritium breeding blankets of the fusion reactor with the best tritium breeding performance; and implementing the global optimal blankets scheme in the tritium breeding blankets of the fusion reactor.