In this paper, we analyzed changes in muscle length of lower limbs during high-heel walking based on the musculoskeletal model. Twenty young healthy women participated in this study. For each subject, the 3D motion analysis was performed for four different cases; walking with flat shoe, 3cm high-heel, 6cm high-heel, and 9cm high-heel. Then the musculoskeletal model, with modified Hill-type muscles, was made from subjects' anthropometric data and 3D motion capture data. Results showed that heel height did not show significant difference in hip joint motion. However, for 6cm and 9cm high-heels, knee flexion increased during loading response due to the insufficient extension of biceps femoris short head. Changes in muscle length of soleus and tibialis anterior significantly decreased and the muscle force of soleus decreased. Our results showed that the ankle joint played most important role to adapt high-heel lower than 6cm, but the contribution of other lower extremity joints, especially knee joint, would be required for the higher heel. Changes in muscle length provided more valuable information to determine gait characteristics in various clinical conditions.