Abstract: In order to reveal genetic basis of heterosis in rice,studies were performed on isozymes of 14 kinds of enzymes in shoots for 6 hybrids and their parents;and isozyme loci were detected for isozyme bands which were clear and stable.Related data to 28 loci were acquired,which include character,phenotype polymorphism of each locus and enzyme activity,average relative mobility of enzyme bands encoded by each locus.No differences were shown among all of the experimental materials on 25 loci,and differences only appeared among 6 hybrids and their parents on 3 loci(i.e.Est-4,Amy-1,Aat-2),in which,isozyme bands of 81.8 percent combinations showed co-dominance phenomena.In addition,the relationships between co dominance and heterosis were discussed.