Abstarct: Improving the rate of germination and crop growth in early season via increasing crop competitiveness can increase the competitive ability of crops with weeds and reduce weed damage. Thus, in order to evaluate the effect of plasma radiation, priming and herbicide application on growth and yield of sunflower (Helianthus annuus L.) and weed control, a factorial experiment was conducted as randomized complete block design with three replications at the research field of Shahrood University of Technology in 2016. Experimental factors were including cold plasma at six levels: control (no treatment), hydro-priming of seeds with distilled water for 10 hours, pretreatment of seeds with plasma radiation for 15 seconds, pretreatment of seeds with plasma radiation for 30 seconds, hydro-priming of seeds for 10 hours + plasma radiation for 15 seconds and hydro-priming of seeds for 10 hours + plasma radiation for 30 second and weed control at three levels: control (no weeding), weeding all season and application of trifluralin(1200 g ai/ha). Results showed that, pre-treatment of seeds by cold plasma increased leaf number per plant, leaf area index, seed number per head and biological yield of sunflower in the presence of weeds than control (no pre-treated seeds) significantly. Leaf and stem dry weight, membrane stability index, carotenoid and seed yield increased by cold plasma and hydro-priming treatments in weed free than weed infest conditions. Total chlorophyll increased by 8.87 and 7.74% in weeding and herbicide application than no weeding treatments respectively. Weed density and biomass decreased significantly by plasma than control treatment and the most decrease was observed in cold plasma radiation treatment for 15 and 30 seconds. baxsed on the results of this study, pre-treatment of seeds by cold plasma could significantly increase the growth characteristics and yield of sunflower through increasing of the crop competitive ability.