Improving the rate of germination and crop growth in early season via increasing crop competitiveness can increase the competitive ability of crops with weeds through enhancing physiological traits. In order to investigate the effect of cold plasma treatment on some physiological and quality traits of sunflower plants in completion with weeds, an experiment was carried out as a factorial in a randomized complete block design with three replications at Shahrood University of Technology in 2016. Experimental factors included cold plasma at six levels: control, hydro-priming of seeds for 10 hours, pretreatment of seeds with cold plasma radiation for 15 and 30 seconds, hydro-priming of seeds for 10 hours + cold plasma radiation for 15 and 30 seconds and weed control at three levels: control (no weeding), weeding all season and application of trifluralin (1200 g. ai. ha^-1). Dielectric barrier discharge plasma jet was operated in ambient air under sterile conditions. After seed priming in distilled water for 10 hours, sunflower seeds were taken in petri plates and treated with the plasma for determined times. Results showed that membrane stability index and carotenoid increased by cold plasma and hydro-priming treatments in weed free than weeds infested conditions. Total chlorophyll content increased by 8.87 and 7.74% in weeding and herbicide application, respectively, compared with no weeding treatments. Sunflower seeds protein percentage increased significantly by application of hydro-priming + cold plasma radiation for 30 seconds compared with herbicide application treatment. Sunflower seed oil percent also increased by using cold plasma radiation for 15 and 30 seconds in weed infested treatments compared with weed free and herbicide application condition. Weed density and biomass decreased significantly by plasma compared with control treatment and the most decrease was observed in cold plasma radiation treatment for 15 and 30 seconds. Based on our results, pre-treatment of seeds by cold plasma and hydro-priming could significantly improve some physiological and quality traits of sunflower through increasing of the crop competitive ability with weeds.