Introduction: It is obvious that all plants adopt mechanisms to control NaCl accumulation because sodium chloride is the most soluble and most abundant salt. Binweed (Convolvulus arvensis L.) is among the ten widespread noxious weeds in the world that it is reproduced by seed, horizontal lateral root, and rhizome. Because of the extensive underground root system of the bindweed with abundant buds and established root reserves, binweed competes more tolerant than crops under salinity and drought stress. More information on morphophysiological traits of binweed under salinity conditions and comparison of salinity tolerance index between germination and seedling can also be contributed to the most effective management. In order to investigate the germination and seedling growth characteristics of binweed two experiments were conducted separately under salinity stress.Materials and Methods: Germination experiment was done in a completely randomized design with 9 levels of salinity stresses include 0 (control), 5, 10, 15, 20, 25, 30, 35, and 40 dS.m -1 , with four replications in the lab. The seedling experiment was performed in a random complete block design consisted of five levels of salinity (tap water, 10, 20, 30, and 40 dS.m -1 ) with three replications as the pot in a non-shade greenhouse of Agricultural College of Shahid Chamran University of Ahvaz.Results: The results showed that with raising salinity, percentage germination and vigure index of seed declined, but Radicle/ Plumule ratio rose. After two weeks, in response to salinity a decrease in root and shoot characteristics of the seedling was observed. Salinity stress data were fitted to a three-parameter logistic for seedling stage showed that the salinity levels higher than 7.86 dS.m -1 led to 50 percent reduction in tolerance index. It was found that 19.84 dS.m -1 caused 50% decrease in the tolerance index at germination stage. Sufficient tolerance index growth stage variation in response to salinity was found which suggests that bindweed tolerance to salinity at germination stage is about 3 times more than that of seedling stage.Conclusions: Radicle/ plumule ratio at germination stage and root lateral branches at seedling stage increased in concentrations of up to 25 and 20 dS.m -1 , respectively. It seems the maintenance of root area and branches in response to increased salinity provide an acceptable mechanism of salinity tolerance for binweed. According to the three-parameter logistic model, the salinity tolerance of bindweed at germination and seedling stages was estimated at 20 and 8 dS.m -1 , respectively.