Arsenic (As) pollution of paddy soil is an important environmental problem of China. Proper measures should be taken to ameliorate or remediate the As-polluted paddy soil in order to increase rice yield and ensure the food security, thereby decreasing the risk caused by As contamination. Recently, biochar has been a research hotspot on preventing and controlling As pollution. However, previous studies mainly focused on the physical and chemical mechanisms on effects of biochar on arsenic migration and transformation. Little is known about the microbial mechanisms of its influence on transformation and bioavailability of arsenic species. In this proposal, various biochar derived from waste will be used with rice as a model plant associated technologies like spectroscopy, analytical chemistry and molecular biology will be adopted to systematically explore the effects of biochar on arsenic transformation and bioavailability in soil especially the rhizosphere soil and its accumulation in rice plant. Moreover, the microbial mechanisms on the influence of biochar on the structure of As-related microbial communities and functional genes of As transformation in rhizosphere soil and As accumulation in rice will also be investigated, in order to understand how biochar affects the environmental behaviors of As and its migration into food chain. The results from this project are expected to provide evidence for decision-making for waste reutilization and As pollution control of paddy soil, risk assessment and safety production of rice and to give technical support on the control of arsenic contamination of paddy soil.