As the offshore wind power gradually moving into deeper water， floating wind turbines are considered as the more economical choices. Helical type floating wind turbine is an optimization of traditional straight-bladed vertical axis wind turbines. This paper presents the dynamic responses of a 5 MW helical type floating vertical axis wind turbine with three blades. The floating foundation is dealt with as a rigid body， and the tower and blades are considered as flexible bodies. A slack coupled modeling method is used to establish the computational model of the wind turbine system， and the numerical calculation code is programed. The dynamic responses of the wind turbine are calculated under combined turbulent wind and irregular waves， and the comparative study is conducted with straight-bladed vertical axis wind turbine. Results show that the aerodynamic torque fluctuations of the helical type wind turbine could be restrained significantly compared with the straight-bladed wind turbine， motions of floating foundation have no apparent difference. Furthermore， the deformations of the tower top point and blade of the helical type wind turbine are obviously smaller than those of the straight-bladed wind turbine. This study could provide a reference on the design of helical type floating vertical axis wind turbines.