Weeds could decrease agricultural productions in different ways like competition for water, nutrients and light, allelopatic effects, interfering in harvesting. Although chemical control creates several problems such as damage to crop, herbicide residues in soil, damage to subsequent crop, and environmental pollution, but all of these problems may be reduced by choosing the right kind of herbicides, timing, amount of herbicide and herbicide`s usage. There is low safflower growth rate in Rosset stage while weeds grow rapidly and compete whith safflower. To recognize of the two preplanting`s effect (trifluralin and ethalfluralin) and their combinations with three postemergence (setoxydim, cycloxydim and haloxyfop) herbicides and also two postemergence (desmedipham and phenmedipham) herbicideds, it was study on control of weeds and growth and yield of safflower at the Lavark Reasrch Farm, Isfahan University of Technology, Isfahan, Iran in 2007. In this study ten herbicide treatments along with the weedy control and hand weeded wich were evaluated using a randomized complete block design with three replications. Also post-emergence herbicides were applied in the 6-8 leaves stage. Furthermore hand weeding was done in hand weeded plots continuously untill the physiological matural stage. The weeds species in the field were identified and number of plants, plant's height and dry matter were measured for the each weed species. To determine the effect of herbicides and the weeds competition on safflower, the height and dry matter of safflower were measured. Samplings were done three times including before the use of postemergence herbicides, at pollination and physiological matural stages. The yield and yield components included head/plant, seed/head, 1000 seed weight were measured and the harvest index were determined. The major weeds in the field were Amaranthus retroflexus , Chenopodium album , Malva neglecta and Covolvulus arvensis . The preplanting herbicides had controlled the weeds totally (100%) and as a effect mostly reduced the whole number, height and dry matter of weeds. The postemergence (desmedipham and phenmedipham) herbicides significantly reduced the height, dry matter, yield and yield components of the safflower compared to the hand weeded and other herbicide treatments. It was reduced due to the weed competition and the herbicide injury to safflower. There was no sign effect on weeds that were studied in this project because they are narrowleaf weed killers. There were no significant differences in the yield of safflower in according to the result of acting of the combination pre and post emergence herbicides, with the hand Keyword : safflower, weed, herbicide, chemical control