Abstract: A new type of semi-submersible platform equipped with a heave plate capable of effectively suppressing the heave motion was designed for floating wind turbines, while its dynamic response to the combined action of wind, wave and flow load was analyzed, which was subsequently compared with that of the three-buoy three-pillar semi-submersible platform. Results show that in the frequency-domain analysis, the heave plate has best suppression effect on the heave motion, followed by the pitch and sway motion; the radiation damping of original platform is closer to that of the heave plate platform in the sway, pitch and heave direction, but the additional mass of the latter is relatively large. In the time-domain analysis, compared with original platform, all the motion responses of heave plate platform are relatively small in the sway, pitch and sway direction, with best suppression effect on the heave motion, followed by the pitch and sway motion.