Objective To propose a method for optimizing the design of diabetic foot insoles by combining the elastic modulus and thickness of footwear to reduce plantar pressure and internal stress in soft tissues. Methods A finite element model of The foot was established using reverse engineering techniques. Orthotic pressure regions were identified based on the characteristics of plantar pressure distributions. Contact mechanics were studied using the finite element method to lay the foundation for adjusting the elastic modulus of the materials and the thickness of the forefoot and rearfoot insoles in different regions during the optimization process. The optimal parameter combination was obtained using an optimal Latin hypercube design. Results The plantar contact area of the designed insole increased by approximately 37.55%, and the peak pressures in the metatarsal and heel regions were reduced by 15.07% and 36.96%, respectively. The internal stress in the soft tissues of the heel decreased by 20.83%. Tension in the plantar fascia decreased by 60%. Conclusions The proposed method can be used for designing customized insoles, and such designed personalized insoles have a greater contact area, with great potential in reducing diabetic foot ulcers.