In order, to evaluate the effects of planting date and plant density on phenology, seed yield and the essential oil quality of Guar an experiment was conducted during 2018-2019 and 2019-2020 growing seasons. The experiments were performed as split plot layout based on a randomized complete block design with three replications. Different planting dates were considered as the main factor included 5th September to 5th February as monthly. Three plant densities were considered as sub-factor (20, 40 and 60 plants in a square meter). The required growing degree- day (GDD) from sowing to physiological maturity was between 1802.3 to 2347.9 °d on different planting dates. The highest GDD from sowing to physiological maturity observed on 5th May. The highest seed yield (3780 kg / ha) and galactomannan yield (1050 kg / ha), 100- seed weight (3.5 g) and the oil percentage (17.9%) were observed on 5th May + 40 plants per m2. by delaying planting time, 100- seed weight and oil percentage decreased and the seed yield (40%), galactomannan (68%) and the oil percentage (15%) were observed on September Therefore, it seems that the best time and density for planting Alyssum is 5th May and the density of 40 plants per m2.