Abstract: The heterosis of seed vigor，the relationships among seed vigor characters，and the changes of seed vigor in F1 during seed development stage were analyzed with six sweet corn inbred lines and their F1 hybrids. The results indicated that seed vigor increased along with seed development and the optimum harvest date was influenced by genotype. The 100-seed weight，germination rate，germination potential，fresh weight of seedlings and vigor index showed significant differences among different genotypes. Vigor index showed significantly positive correlations with germination rate and germination potential，and no significant correlation with 100-seed weight. The 100-seed weight of F1 seeds showed negative heterosis and significantly positive correlation with female parent，while the vigor index had positive heterosis and affected by low-vigor parent significantly. It was suggested that 100-seed weight and seed vigor of F1 seeds could be improved by applying female parent with high 100-seed weight and avoiding using low vigor parent.