By quantitatively studying the response of Populus euphratica population growth and plant diversity to flooding irrigation in lower reaches of Yarkant River basin,a theoretical basis for optimizing water resource management regulation and ecological protection practice in Yarkant River Basin is provided. From 2016 to 2018,Three visits were paid to the lower reaches of Yarkant River to obtain vegetation survey data,and to analyze the response of Populus euphratica population to flooding irrigation with the aid of Pielou index,Shannon-Wiener index,Simpson index and important values. The results show that after 2 a of flooding irrigation the Simpson index,Shannon-Wiener index and Pielou index increased by 124.8%,119.6% and 246.9% for Populus euphratica forest in lower reaches of Yarkant River,respectively,and 12 new species of hygrophilous and annual herbaceous plants were found,and vegetation coverage rate was 42.5%,increased by 112.5%. Populus euphratica forest in the study area were medium aged,growth of Populus euphratica did not deteriorate,growth of Populus euphratica forest above medium grade increased by 3.9%,and the height under the crown of Pop-ulus euphratica decreased by 7.7%. With the increase of distance from ecological gate,plant density and diversity had a decreasing trend,but 450 m distance from ecological gate the plant diversity and plant density was significantly higher than that of the plants with 150,300 and 600 m from ecological gate (P<0.05). The dominant species at 150 and 300 m in distance to the ecological gate were annual herbaceous and hygrophilous plant such as Sophora alopecuroides and Phrag-mites australis,etc. Outside the range of 450 m in distance the dominant species were Populus euphratica,Tamarix ra-mosissima and drought-tolerant perennial herbaceous. The 2 a flooding irrigation project ended the tendency of Populus eu-phratica forest degradation,and significantly improved plant diversity and vegetation coverage. At the same time,plant community of desert riparian forest has enhanced its ability to renew within 450 m in distance to the irrigation gate,and biodiversity has been protected. In order to maintain current trend of ecological improvement,flooding irrigation projects should be continued.