Objective To investigate the biomechanical characteristics of lower extremities of competitive taekwondo athletes during double roundhouse kick ( DRK) with the use of electronic body protector ( EBP). Methods Fourteen competitive taekwondo athletes were recruited, and their kinematic, kinetic and surface electromyogram (sEMG) data of lower limb joints during DRK with effective scoring were collected by electronic guard scoring system, sEMG testing equipment, three-dimensional (3D) motion capture equipment and 3D force plate. The motion time, center of gravity ( COG) displacement, range of motion ( ROM) and velocity of lower limb joints, ground reaction force (GRF) and other parameters were calculated by Visual 3D software. Results The total time for two strikes of DRK was 0. 583 s and the attacking period of both dominant and non-dominant sides was the same. The shift of COG was smaller during the kick, and both dominant and non-dominant sides had good balance control ability. The trends of changes in hip, knee, and ankle joint motion angles and angular velocities of the two limb sides were consistent. In knee flexion phase before striking, the deficiency of knee flexion angle of the attacking leg could be achieved by increasing the extension angular velocity in extension phase. In knee flexion and extension phases before striking, the medial head of the lower extremities gastrocnemius muscle generated the most power on two limb sides. Conclusions The DRK technique has good continuity and left-right symmetry, and it can contribute to scoring by reducing the time of attack during the second striking. Athletes should strengthen the ankle joint flexibility, as well as gastrocnemius and gluteus maximus in training process of DRK movement, so as to avoid unnecessary sports injuries and be more adaptable to game mode with the use of EBP.