In order to study the mechanical characteristics of human tibia in motion state, accurate CT data of lower limbs of healthy volunteers were collected, and then precise human tibia finite element model with axial functional gradient was constructed by MIMICS. The stress distribution and displacement deformation of human tibial movement were simulated and analyzed in ANSYS Workbench. The stress distribution and displacement study of dynamic knee valgus flexion compared with normal posture of tibia show that: ①Stress concentration in the normal posture group occurred mainly on the frontal aspect of the middle and lower tibia, whereas in the dynamic knee valgus group it occurred mainly on the medial surface of the middle tibia.②The maximum von-Mises stress in the dynamic knee valgus group increased by 38.8%, 39.65%, 34.95% and 27.52% compared to the normal posture group in the four flexion angles respectively.③For the tibial plateau, the maximum von-Mises stress of the medial tibia was greater than the lateral tibia in the normal posture group and the lateral tibia greater than the medial tibia in the dynamic knee valgus group. The stress distribution in tibia was altered and the maximum von-Mises stress was significantly increased from normal posture to dynamic knee valgus flexion. The middle tibial and the lateral tibial plateau are vulnerable areas, dynamic knee valgus posture should be avoided in daily life and sports.