The rice parents with lower grain mass per panicle and 1000-grain mass CB1, CB7 and the higher parent CB4 were chosen to construct the combines CB1×CB4 and CB7×CB4; also the corresponding P₁，F₁，P₂，B₁，B₂，F₂populations were established and planted as middle and late two planting seasons and the mass per panicle and 1000-grain mass traits were checked, respectively. The Akaike’s information criterion (AIC) of the major genes plus polygenes mixed inheritance model was used to identify the existence of major genes affecting quantitative traits in B₁，B₂，F₂populations, and when the major genes existed, the genetic effects of the major genes and polygenes and their genetic variance were estimated through segregation analysis. The results showed: One major genes plus polygenes was the most fitted genetic model for grain mass per panicle in the all B₁，B₂，F₂ populations. The heritability values of the major genes varied from 58.06% to 75.60% and those of polygenes varied from 5.03% to 25.46%, and the total heritability values were from 68.07% to 96.68%. The heritability values of the same genetic population under the different planting seasons showed little difference, while those of population of combination of CB7/CB4 were higher than those of population of combination CB1/CB4 of the same planting season. The findings suggested that parents selection constructing the genetic population should be considered when analyzing the heredity of the grain mass per panicle trait. One additive major gene plus additive-dominance polygenes was the most fitted genetic model for 1000-grain mass in the all B₁，B₂，F₂ populations. The heritability values of the major genes of population of combination CB1/CB4 as middle season planting were the highest in the two genetic populations of the two planting seasons and varied from 60.06% to 69.38%. While the polygenes heritability values of population of combination CB1/CB4 as middle season planting were the lowest and varied from 10.70% to 23.21%. The total genes heritability values of population of combination CB1/CB4 as middle season planting was varied from 71.48% to 83.55%. The first order parameter d value of population of combination CB1/CB4 as middle season planting was the lowest in the two genetic populations of the two planting seasons, which suggested that parents selection constructing the genetic population should be considered when analyzing genetic of the grain mass trait.