Abstract: Microplastics is widely distributed in the marine environment and accumulates continuously in the environment and biota, which has a severe impact on marine biota. This new and emerging issue has attracted the attention of scholars, administrators, nongovernmental organizations and other social circles in the world. Marine microplastic pollution is a new research field which has been developing rapidly in the past ten years, and has become the hot spot and frontier in the international scientific community. However, there are still some knowledge gaps between China and other developed nations. This article reviewed the progress in the marine microplastics pollution research, and analyzed the main gaps between China and other developed nations. Three key problems of the marine microplastic pollution research are classified as temporal and spatial distributions, physicochemical properties, and the biological and ecological effects of microplastics in marine environment. It suggested that more standards and innovation in research methodologies, technical means, index for hazard evaluation around the three key problems are required to promote developing marine microplastics pollution research in China.