The present research was conducted in order to investigate the effect of cover crops in density and different planting dates on weed control and soybean yield. The experiment was conducted as a factorial design in the form of a randomized complete block design with three replications during growth seasons of 2020-2021 and 2021-2022 in the research farm of the Agricultural and Natural Resources Research and Training Center of Ardabil Province (Moghan). The studied factors include the date of planting cover crops in two levels (at the same time and three weeks after soybean planting), their planting density in two levels (recommended and triple recommended) and the type of cover crop in 12 levels (including autumn barley, oats, autumn rye, autumn wheat, berseem clover, Persian clover, crismon clover, yellow sweet clover, red clover, annual alfalfa, chickling pea and hairy vetch). Also, two control treatments were considered in the form of pure soybean cultivation (without cover crop cultivation) along with spraying and without spraying against weeds next to each replication. The variance analysis of the data showed that the simple and intraction effect of the study treatments was significant in most of the traits. The lowest density of weeds was related to the treatment of hairy vetch in between the rows of soybeans in the second year and on the second date (at the rate of 5.78 plants per square meter), which was achieved with the berseem clover treatment in It was a common statistical group. The lowest amount of weed biomass was also obtained in the treatment of berseem clover among soybean rows on the second planting date and the triple recommended planting density of 3 grams per square meter. All the cover crops studied had the highest biomass on the first sowing date and the triple recommended.. berseem clover with the highest biomass production (137.02 grams per square meter) was ranked first. The highest percentage of soybean oil was obtained in the second year and on the first date and the second density (23.79%). Among the cover crops, the cultivation of hairy vetch among the rows of soybeans, due to its fast growth and greater adaptation to the region, minimal competition with the main plant and also better control of weeds, causes a greater increase the plant height, biological yield, seed protein percentage, seed yield and soybean harvest index were measured. Finally, the maximum yield of soybeans was obtained on the second planting date and triple recommended density in the cover crops of the hairy vetch at the rate of 3616 kg per hectare.  Therefore, it is recommended to use this cover crop in order to achieve the goals of sustainable agriculture in these areas.