Microplastic particles,defined as plastic particles smaller than 5mm,are derived from the fragmentation of larger debris or enter the environment directly as microplastic fragments.The pathways of microplastic ingested by marine organisms and its effects to marine ecosystem have aroused worldwide attention.This review discusses the sources,types and distributions of microplastic in marine environment stress that there are plastic particles floating on coastal and marine environment in the world,while in China,coastal areas are the main polluted areas. Microplastic particles threat various marine organisms including fish.The main pathway that marine fish accumulate microplastic is ingestion by mistake.Plastic particles are mainly found in the digestive tract of several fish species. The ecotoxicological effects of microplastic on fish include:decrease survival,affect development and reproduction, disturb behavior,lead to tissue lesion and inflammatory reaction,cause metabolic disorder,damage nervous system,induce oxidative stress and interrupt endocrine.In the future,several aspects need to take more attentions on the effects of microplastic research,especially the difference between microplastic used in laboratory experiment and natural environment,such as concentrations,shape and size.Furthermore,international cooperation should be strengthened for observing the migration and transformation pathway of microplastic in marine ecosystem as well as investigating the ecological effects of microplastic and their internal mechanisms on marine organisms and ecosystem.Meanwhile,the joint toxicity of microplastic with other marine pollutants should be valued and its interactive effects with global climate change,such as high tempeture,ocean acidification and hypoxia should be further investigated.