Abstract: Objectives The Blended-Wing-Body (BWB) underwater glider is prone to structural damage during the lifting process. To ensure its structural safety and achieve the goal of lightweight design, the internal pressure-resistant cabin fixing bracket is optimized. Methods A multi-fidelity data-driven optimization method is adopted, combined with structural parametric modeling method and finite element method, to carry out the structural design of the internal pressure-resistant cabin fixing bracket of the BWB underwater glider. A high and low fidelity numerical model of the fixing bracket structure is established, and a multi-fidelity data-driven optimization method based on the hierarchical Kriging model is proposed. Based on this method, a fully automatic optimization design framework for the cabin fixing frame is constructed, and the optimization design of the cabin fixing frame is completed. Results The results show that, while ensuring structural safety, the mass of the optimized cabin fixing bracket is reduced by 16.4%. Compared with the particle swarm optimization algorithm, the proposed optimization design method can reduce computational cost by 75% when obtaining the same level of optimization design results, greatly improving the efficiency of optimization design. Conclusions The research method and conclusion provide an efficient optimization design approach for the structural design of the pressure-resistant cabin fixing bracket of the BWB underwater glider.