Objective The purpose of this study was to explore the joint contact force, ligament tension and force conduction mode of foot internal structure in Down syndrome children (DSC) during standing. Methods Two three-dimension finite element foot models were constructed based on the CT of the DSC and typically developing children (TDC). The model validation was conducted by comparing the plantar pressure in finite element analysis with in-vivo plantar pressure measurement from the same participants during standing. To simulate standing, the ground reaction force of standing and the triceps surae force were taken as the loading condition. The analysis outcomes included: the contact pressure of the tibiotalar, talonavicular, and calcaneocuboid joints, tensile force of spring and plantar calcaneocuboid ligaments, and force transmission in transverse tarsal joints. Results The finite element models of foot were validated and reliable. Compared with the TDC, the DSC showed higher contact pressure at the tibiotalar joint (0.81 vs 0.61 MPa) and lower contact pressure at the talonavicular joint (0.34 vs 0.64 MPa). The tensile force of spring and plantar calcaneocuboid ligaments of DSC was 10 times and 58 times of TDC, respectively. The forces transmitted through both mediate and lateral columns in DSC was lower than those in TDC. Conclusions The abnormal contact pressure of tibiotalar joint, larger tension of midfoot ligaments and smaller force of transverse tarsal joint were found in DSC during standing. The abnormal alteration of stress pattern in the foot of DSC should be fully considered in clinical rehabilitation to screen early rehabilitation interventions and design orthopedic insoles.