Objective To investigate the biomechanical effects of the whole hardening of plantar soft tissue and the local hardening under metatarsal heards and calcaneus on human foot and ankle system. Methods Buliding a 3D finite element model based on the MRI scanning pictures of a healthy young volunteer and changing the material property of plnatar soft tissue to simulate different plantar soft tissue status; and three solutions simulatng the balanced standing were done to compare model’s prediction. In addition, the plantar pressure measurement of the volunteer was used to validite the model. Results The foot model was created and validated. Three solutions were completed under different material properties of plantar soft tissue, and the contact pressure distribution and some mechanical information of internal soft and hard tissue were quantified. Conclusion The hardening of plantar soft tissue, especially the local hardening, greatly affects the contact pressure distribution and stress magnitudes in plantar soft tissue, which would increase potential risk of plantar ulcer.