Abstract: Grain traits were related with rice yield and quality. A better understanding toward the underlying inheritance basis of grain traits would guide molecular breeding. Based on the major genepolygene mixed inheritance model， we performed a genetic segregation analysis for the grain traits i.e. grain length， width and weight， with P1， P2， F1 and F2 in the cross of rice cv. 3012 and cv. Wantedali. The results showed that both grain length and grain width were controlled by one major gene with additivedominantepistatic effects plus polygene with additivedominantepistatic effects， while grain weight was regulated by 2 major genes with 2 additivedominantepistatic effects plus polygene with additivedominantepistatic effects. The inheritabilities of grain length and grain width were mainly dominated by polygene， while grain weight was dominated by major gene. For all the 3 grain traits studied， additive effects were principal．

Key words: rice, grain length, grain width, grain weight, inheritance