The aim of this study was to screen low phosphorus-tolerant oat （Avena sativa L.） varieties and to investigate their morphophysiological response mechanisms. Thirty oat varieties were used as materials， and two treatments of normal phosphorus （1000 μmol·L^-1 KH₂PO₄， CK） and low phosphorus （10 μmol·L^-1 KH₂PO₄， LP） were set up by hydroponics. Morphological and physiological indexes were measured after 21 days， and principal components， subordinate functions， and cluster analyses were used for the comprehensive evaluation. The results showed that low phosphorus stress significantly inhibited the aboveground growth of most oat seedlings， but promoted root development. Physiologically， low phosphorus treatment led to a decrease in phosphorus uptake and a significant increase in phosphorus utilization efficiency in most seedlings； soluble sugar content， acid phosphatase and nitrate reductase activities generally increased. Through systematic evaluation， ‘Weidu You No.5’ （D=0.818） and ‘Jin Yan No. 17’ （D=0.643） were identified as the most low-phosphorus-tolerant varieties， whereas ‘Ba You No. 18’ （D=0.341） and ‘Jun Ma’ （D=0.366） were the most sensitive ones. The results of this study provide a theoretical basis and material foundation for the selection and breeding of low phosphorus tolerant oat varieties.

Avena sativa  /  Low phosphorus stress  /  Morphological index  /  Physiological response  /  Low- phosphorus tolerance evaluation