The utilization of tidal stream energy has become one of the hot research topics in the field of ocean renewable energy. In this study, the distribution status of tidal stream energy resource and classification of tidal stream energy converter(TSEC)were summarized, and the current main demonstration projects of tidal stream energy at home and abroad were introduced. The key technologies of TSEC including the assessment of tidal energy resources, the safety and stability of TSEC, the utilization efficiency and multi-complementary of ocean renewable energy, the wake effect, and the environmental impacts of TSEC array have been discussed. Although the development of TSEC is feasible and necessary, there are still many challenges and difficulties to be solved.