Abstarct: This experiment was performed to investigate the effect of foliar application of amino acid mixture on some growth traits, forage and grain yield of three cultivars of Sorghum (Sorghum bicolor L.) in competition with weeds in a factorial experiment baxsed on a randomized complete block design with three replications at the research farm of Shahroud University of Technology in the growing season of 2018-19. Experimental factors were including sorghum cultivars at three levels: Aresk, Speedfeed and Pegah, and foliar application of amino acids (megafol) at three levels: control or non-treatment, application of 1 and 2lit /ha and third factor including weeding and non-weeding of weeds. The results showed that with the use of amino acids, the content of chlorophyll a, b and carotenoid increased significantly than control. The highest relative leaf water content was observed by application of 2lit/ha of amino acids in weeding condition. By using amino acid, stem diameter, plant height and leaf area index of sorghum increased significantly compared to the control. Grain and leaf protein significantly improved by using amino acid than control. The highest percentage of grain and leaf protein (5.9 and 8.7 percent respectively) observed in Aresk cultivar. The highest dry forage of sorghum with 17.5 ton/ ha was belong to application of 2lit/ha amino acid in weeding treatment, and found that it increased by 10 percent than control. The most amounts of grain yield observed in foliar spraying of 2lit/ha amnio acid and weeding with 7.9 ton/ha, found that it increased by 29.5 percent than control. The lowest dry weight of weeds was observed in local cultivar and application of 2 lit/ha of amino acid. In general, weeds reduced the various traits measured in this experiment, but the application of amino acids by improving photosynthetic pigments, relative water content and agronomic traits of the plant could improve the growth status of the sorghum and its competitiveness with weeds. baxsed on the results of this experiment, the use of amino acids and more competitive cultivars as non-chemical strategies can play a role in achieving the goals of sustainable agriculture in the production of forage and sorghum seeds.