Taking winter wheat cultivar ‘Yunong 211’ as materials, we carried out a pot experiment that set up to control water for 12 days and rewater for 2 days after drought to study the effects of root application of 15 mmol·L^-1 propionic acid on plant morphology, leaf relative water content, electrical conductivity, malondialdehyde content and the dynamic changes of leaf proline content and its key metabolic enzyme activities, to explore the mechanism of proline metabolism of exogenous propionic acid in improving drought resistance of wheat. The results showed that: (1) under drought stress (the relative water content of soil decreased to 20%), the root application of propionic acid could significantly increase the relative water content of wheat leaves, and reduce the relative conductivity and malondialdehyde content of wheat leaves. The wilting degree of wheat seedlings treated with propionic acid was significantly lower than that of control, and the biomass accumulation in the shoot increased by 13.3% (P < 0.05). (2) Under mild water stress (soil relative water content decreased to 45%-55%), the root propionic acid treatment led to a significant accumulation of proline than control. With the increase of drought stress (soil relative water content decreased to below 20%), it could still maintain at the normal level (about 300 μg·g^-1), while the proline content in control leaves increased sharply; and the proline content in leaves of wheat treated with propionic acid could recover to normal level rapidly. (3) During the whole process from water control to rewatering, the activities of the key enzymes Δ 1pyrroline5carboxylate synthetase (P5CS) and ornithine aminotransferase (σOAT) of proline biosynthesis increased firstly and then decreased. The activity of pyrroline5carboxylic acid reductase (P5CR) decreased firstly and then increased, while the activity of proline dehydrogenase (PDH), the key enzyme of proline degradation, increased. These results suggested that under drought stress, applying propionic acid to roots could regulate the key enzyme activities of proline synthesis and degradation pathway in the process of proline metabolism to maintain the stability of proline level in leaf cells, and effectively reduce the degree of water loss and peroxidation damage of leaves, so as to improve the drought resistance of winter wheat seedlings.