A field experiment was conducted in field located in Ramadi city during the growing seasons of 2010 and 2011, to evaluate the potential variations in growth traits of some soybean cultivars and its impact on their competitive ability to accompanied weeds. The experiment was accomplished using randomized complete block design (RCBD) in split- split plot arrangement with three replicates. The study involved four weed treatments (weedy, weed free, herbicide spray at recommended and half of recommended concentration) as main treatments, whereas, sub plots involved two crop densities (400000 and 266666 plant.ha-1). Sub-sub plots comprised of four soybean cultivars (Ls 75, Lee 74, Giza 111 and Giza 35).Results revealed a clear effect of different weed treatments on most studied traits. Herbicide treatments at recommended concentration with cultivar G111 achieved least mean of weed density (17.36 and 20.69) plants.m-2 for both seasons, respectively compared with other cultivars spraying of herbicide at the recommended concentration with some cultivar achieved the highest percentage of weed control 57.0 and 50.8%,. For soybean cultivars, Giza 111 characterized with its ability to reduced weeds density and increased control percentage of the accompanied weeds in a degree better than other cultivars under study. This cultivar achieved higher values for No. of branches (5.61 and 5.99 branch. Plant -1) and leaf area (56.25 and 67.05 dm2.plant -1) for both seasons, respectively. This gave an indicator that this cultivar had an ability to tolerate weed competition comparing with other cultivars. Most of soybean cultivars showed a response to the different treatments of weed control higher than their response to crop densities in reducing accompanied weed density. However, weed density significantly decreased in the highest crop density (D1) comparing with lowest crop density (D2) during the same periods 60 days in both seasons. From the recent study it can be concluded that the variation among soybean cultivars in most of vegetative growth traits could be used as criater in for their competitive ability to accompanied weeds.