Nine soybean cultivars representing most of known matunty groups were cultivated at four planting dates, i.e. I 15 tu May, I and 15 th. June at the Experimental Station of National Research Center at Shalakan Kalubia Governorate to study seed filling in certain soybean cultivars. The results indicated that soybean cultivars significantly differed in seed filling rate (g/day) and effective filling period (days). Moreover, Maximum filling rate was achieved at 54-61 and 68-75 days from sowing, at mid June, at 82-89 days after sowing time at first June and at 96-1 03 and 110-117 days from sowing resulted from sowing so’bean in 15 th May and I May date, respectively. Meanwhile, sowing date in 15 th May gave the maximum effective filling period.