In order to investigate the effect of different amounts of soil moisture in different salicylic acid levels on enzymes activity and morphophysiological characteristics of alfalfa, a factorial experiment was designed and conducted in a randomized complete block design with three replications at the Agricultural Research Station of Kurdistan University in summer 2013 in a field condition. The first factor included two levels of normal irrigation (100 percent field capacity) and drought tension (50 percent field capacity) and the second factor included five levels of foliar application of salicylic acid (0, 7, 21, 35, and 49 percent). The results indicated a significant effect of drought tension and foliar application of salicylic acid interaction on biologic yield, leaf number, leaf area, photosynthetic pigments (P<0.01), the activity of Ascorbate Peroxidase Enzyme(APX) and biosynthesis of proline (P<0.05). Salicylic acid application at each irrigation level improved growth and increased activity of ascorbate peroxidase enzyme and proline content of leaf, that this positive effect was more than control treatment under tension conditions, so that dry forage yield in normal irrigation level and drought tension with 7289 and 5871 kilogram per hectare allocated to treatments 21 and 35 percent levels of salicylic acid, respectively, that increased 19.93 and 53.62 percent compared to control treatment. In general, drought tension reduced grain yield and its related traits, while Salicylic acid application could compensate product yield loss relatively through the effect on increasing proline synthesis, enhancing plant water potential, and photosynthesis.