Six populations of four soybean crosses (L-86-K-96 × Ware), (Egyptian ×Ware), (H129 × Crawford) and (DR101× Giza 111) were conducted during three successive summer seasons 2019, 2020 and 2021 at the experimental farm of Sakha agricultural research station (SARS), Kafr El-sheikh, Egypt for estimate the adequacy of genetic model and types of gene action for earliness, seed yield and its attributes. The scaling test provides evidence of non-allelic interaction in controlling all characters in all studies crosses. The additive, dominance and their digenic interaction types, additive x additive and dominance x dominance gene effects were significant and involved in the inheritance of days to 50% flowering in all crosses, days to 90% maturity and 100 seed weight in 1^st cross, plant height in 3^rd cross and number of pods/plant in 1^st and 4^th crosses. Duplicate type of epistasis was registered in 3^rd cross for plant height; 4^th cross for number of pods/plant; 1^st and 2^nd crosses for 100-seed weight and 1^st cross for seed weight /plant. Heritability in narrow sense was high for plant height and seed weight /plant in 2^nd cross and number of pods/plant in 3^rd one. Positive and significant heterosis relative to mid and best parent were detected for number of pods/plant, number of seeds/plant and seed weight /plant in all crosses. Positive and significant correlation was detected between seed weight /plant and each of number of pods/ plant and number of seeds/plant. Number of seeds/plant, 100-seed weight and number of pods/plant had the highest direct effect on seed weight /plant.