Abstarct: Nowadays, the application of antioxidants and plant growth regulators has been discussed for decreasing the negative effect of different stresses. Ascorbic acid have been substance caused witch the resistance to biotic and abiotic stresses. To evaluate the effect of foliar application and seed pretreatment of ascorbic acid on growth and yield of sunflower (Helianthus annus), a field experiment design was carried out in split plot factorial baxsed on randomized complete block in shahrood university in 2012 . Three levels of irrigation, including 8 days interval (well water), 12 days interval (moderate stress) and 16 days interval (severe stress) and sub-factors were three in foliar application ascorbic concentration (0, 15 and 25 mM) and concentration pretreatment of ascorbic acid (0 and 20 mM). Stress treatment applied after plants establishment completely. The foliar application of ascorbic acid was performed in 47 day after sowing respectively. Also, the pre-treatment, the seeds for 24 hours in a solution of 20 mM ascorbic acid were estimates. Results showed that increasing irrigation intervals reduced anthodium dry weight, Stem height, stem diameter, 1000 seed weight, seed oil and seed protein content. With increasing concentration of ascorbic acid foliar application LAI was increased. The highest LAI was obtained from foliar application with concentration of 25 mM With an average 4/2, was higher the 66/41% than non- foliar application. Interaction between stress and foliar application concentrations of ascorbic acid on all traits except stem diameter, head diameter, seed yield, oil and protein yield were significant. The highest shoot dry weight (237/59 gr/m2) of non-stress and non-foliar application conditions, and the highest percentage protein (33/09) of non-stress and foliar application 15 mM conditions obtained. Pretreatment with concentration of 20 mM ascorbic acid in moderate stress conditions had a positive impact on oil and highest value created compared to pretreatment with concentration of 20 mM ascorbic acid in non-stress and sever stress conditions raising the 3/22 and 19/31 percent respectively. The intraction between ascorbic acid foliar application with 25 mM concentration and pretreatment with concentration of 20 mM ascorbic acid in non-stress and sever stress condition has the highest effect on investigated traits.