Through researching on Taijiquan Needle at Sea Bottom motion process human postures status, it provides space image basis for knee joint force analysis and knee joint relative segments movements’ dynamical analysis. Apply rigid mechanics theory and Lagrange’s dynamical equations; analyze knee joint force status and human lower limbs motions dynamical equations that provides theoretical basis for knee joint injury causes. Utilize digital camera and three dimensional force platform system and other equipment, collecting habitual position posture, stand position posture and right knee minimum joint angle posture these three postures knee joint biomechanical parameters, get that human stand position and habitual postures right knee joint muscle torques have very significant differences, and habitual position muscle torque is 1.07 to 2.06 times higher than that in stand position. When human in habitual posture, its knee joint stability mainly relies on quadriceps femoris and ligament to maintain; and knee joint get flexion in habitual position would let quadriceps femoris excessive stretch that easier to wear it down causing patellar ligament also prone to get injured .Under habitual postures and right knee minimum joint angle postures such two postures, when joint angle becomes smaller, muscle torque would get bigger and gravity torque get bigger, muscle torque would increase accordingly. Through researching Taijiquan Needle at Sea Bottom motion process knee joint injury status, it provides better theoretical support for physiological analyzing, and make reasonable suggestions for injury prevention.