The purpose of this study was to determine the biomechanical effect of wearing the mouthguard on the lower limb during drop landing. Nine male university students who have no musculoskeletal disorder were recruited as the subjects. Linear velocity, angular velocity, vertical GRF, loading rate, joint moment, and lower extremity muscle activity were determined for each subject. For each dependent variable, paired t-test was performed to test if significant difference existed between with mouthguard (WM) and without mouthguard (WOM) conditions (p<.05). The results showed that linear velocity, angular velocity, vertical GRF and loading rate were no significant difference between the two groups. The inversion moment of the ankle joint was increased in WM compared to WOM. Average IEMG values from BF, TA, and LG in WM were significantly greater than corresponding values in WOM during IP phase. This indicates that wearing mouthguard played a vital role in muscle tuning for maintaining joint stability of the lower limb and preventing injury.