Tidal current turbine is the core equipment to convert the tidal current energy. In this paper, the performance of the designed tidal current turbine is tested in the laboratory, then the impeller is used to conduct an experiment on the desalination of sea water. The sea test of the novel equipment has been done in BoHai Sea. The experimental results indicate that the efficiency of the newly developed turbine could reach up to 47.6%; the corresponding tip speed ratio is from 3.5 to 6. Under the condition of big yaw angle, the turbine could still remain high working efficiency. When the tidal current velocity exceeds 1.0 m/s, the pressure may increase to 3.5 Mpa, and under this condition, sea water can be desalinated through reverse osmic membrane. The electrical conductivity of desalinated water is around 540 μS/cm. For the experiment on hydrodynamic performance, the self‐starting flow velocity of the turbine is 0.745 m/s, the staring torque is 1 Nm while about 0.97–1.0 m/s self‐starting flow velocity and around 10–15 Nm starting torque for the experiment on desalination of sea water. It is believed a good attempt by using tidal current turbine in the desalination of sea water, providing the practice basis on expanding the utilization of ocean energy.