Objectives: To research the regulation mechanism of As resistance in rice and indentify the role of miR399 in the response to As stress through transgene technology and Rip-seq.Methods: Seeds of Nipponbare and STTM399(low expression of miR399 transgenic lines)were preserved in the laboratory and cultivated in the science and education district of Henan Agricultural University,Zhengzhou,China in 2015.The As treatments were setted two levels,plants and seeds were harvested to tested the expression of miRNA and As content.Results:Under the stress of As,low expression of miR399 transgenic lines in arsenic levels were elevated,phosphorus uptake was reduced,miR399 expression change is not obvious,the expression of miR399 in wild-type plants increased significantly.Rip-seq showed that the expression of miR399 in rice grain was significantly increased under As stress.Conclusion: miR399 is involved in the mechanism of As uptake in plants,and it is of great significance to study the regulatory effect of miR399 on arsenic uptake and transport from molecular level.