Abstract: Analysis on seed, cytoplasmic and maternal genetic effects for soluble sugar content (SSC), total nitrogen content (TNC), ratio of sugar to nitrogen (RSN) was conducted by using genetic models for quantitative traits of seed in cereal crops. According to complete diallel cross design, parents, F1 and F2 genetic generations derived from six different types of rice varieties (parental lines), were used for this experiment. The main results were as follow. Analysis on genetic variance showed that all the traits were controlled by genes of seed, cytoplasm and maternal plant simultaneously. SSC was mainly affected by dominant effects of diploid maternal nuclear genes, while TNC and RSN by dominant effects of seed nuclear genes. The results of heritabilities analysis indicated that heritabilities for SSC and RSN were small or depressive, implying that selection for them might be invalid. Direct heritability for TNC appeared to be large, for which single seed descent method might be better in genetic selection.