Abtract：Flue-cured tobacco high-yielding varieties ‘Shubalaomuji’, ‘Taiyan-7’ and the low-yielding varieties TI245 formulated into two crosses, respectively and got six generations plants( P1, P2, F1, F2, B1, B2). Principal Gene Mixed Genetic multiple generations combined method was used to analyze genetic effects of two combinations’ yield traits at different growth stages. The results showed the number of expressing genes and genetic effects , which played regulatory roles in the construction process of two combinations yield traits, existed differences in the developmental stages. The additive effect and dominance effect existed in the entire development process, while the extents of the effects at the different growth stages were significantly different. At the same time the additive ?additive, dominance ?dominance interaction effects performed strong performances during the development of yield traits, but expressed intermittently with the growth stage changing. With distinct genetic effects of the different growth stages, phenotypic variation of squaring stage was decided by genetic effects to more degrees than the other two growth stages, less impacted by the environmental. And the genetic effects of the two combinations also existing significant difference, combination Ⅱ was higher than combination Ⅰ. Major gentic plus polygentic effects of different combinations’ yield trait at the different growth stages were significantly different, under different environmental impact. It is necessary not only to consider gene effects in the breeding work, but also pay attention to the environmental impact.