Development of marine energy is important for the construction of a powerful marine country. This paper discusses the contribution of scientific and technological innovations to the exploration and development of marine energy in recent years, and puts forward the main direction and suggestions for China's marine energy development in the future: to increase the technological research of offshore unconventional oil and gas development to provide more practical contribution for China's oil and gas industry; to increase the exploration and development of deep-water oil and gas for future replacement area; to break through key technology of large-scale development of natural gas hydrate and realize commercial exploitation as soon as possible; to build a fleet of deep-water energy development equipment to support the construction of a powerful marine country; to seize the opportunity to lay out and promote exploration and development of ocean minerals; and to further strengthen polar scientific research and deep participate in polar development.

This paper reviews the technical progress of power generation devices of tidal energy, tidal current energy, wave energy, ocean thermal energy and salinity gradient energy in China. The 4.1 MW Jiangxia tidal power station, 650 kW tidal current energy power station of Zhejiang University, 500 kW wave energy power station of Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences and 15 kW ocean thermal energy power station of First Institute of Oceanography, Ministry of Natural Resources are compared with the advanced marine energy equipments abroad in terms of the scale and the key technical parameters. The results show that the energy conversion efficiency of power generation is close to the international advanced level, but there are still some gaps in the installed power, sea trial time and device reliability. Then this paper suggests that the research and development of common technology of marine energy devices should be carried out at the same time of developing the key technology, so as to improve the reliability and safety of marine energy equipments. Researches on green technology and comprehensive utilization of marine energy should be carried out actively to promote the transformation of key technologies of marine energy, and to promote industrialization of marine energy equipments.

China is a big marine country， its fishery plays an important role in economy, and people's food composition. It is a big challenge for China to solve the contradiction between decrease of global fishery resources and increase of demand for marine products, and the conflicts between sustainable output of marine production and deterioration of marine environment. To explore a way of sustainable marine fishery is always a global challenge. This article is to present a promising way in establishment of sustainable fishery by building sea ranches, and the relative concept, strategy, methods, management policy, etc. are discussed.

This paper reviews the current hot issues in the research of marine microplastics and points out the defects in the methods of sample collection and analysis, as well as the reason for misconceptions in people's scientific cognition of marine microplastics. Moreover, this paper objectively analyzes the shortcomings and mistakes in advanced research areas such as microplastic toxicology, plastic flux into the sea, and environmental risk assessment. It also introduces some new research ideas and progress. Finally, some important scientific questions in the study of marine microplastics and some suggestions for future research development are put forward.