Objective For the research of relative motion and dynamic biomechanics of knee joint during squat. Providing the data of relative motion and biomechanics of knee joint for research of bio-tribology Methods Dynamic finite element (FE) model of knee and after total knee replacement (TKR), which include tibio-femoral, patello-femoral articulations and the surrounding soft tissues, were developed in this research, to simulate both the kinematics and the internal stresses during squat simulation. The kinematic simulating results and the contact stresses distribution of a full deformable contact analysis of knee and prosthetic knee joint during squat, were verified by comparing with the data from an unique experiment. Results The dynamic 3D relative movement data and the contact distribution and stress of both tibiofemoral and patellofemoral joint in dynamic deep flexion were obtained.The results showed that relatively higher contact stresses were distributed in three different areas: the interface of cam-post and the anterior tibia insert, medial-posterior tibia insert and posterior tibia trabecula. These were also main areas with high wear rate Conclusion The established dynamic FE models are capable of predicting the kinematics and the stresses during squat，and could be a efficient tool for the analysis of TKR, research of bio-tribology and knee prosthesis design.