Though the fact that whether selenium (Se) is an essential element for rice plants is not confirmed now, many previous studies focused on the characteristics of Se accumulation in common rice grains through application of Se fertilizers to soil. To further understand the quality of Se in the Se-enriched rice cultivars, a Se-accumulating rice cultivar (Fengbazhan) cultivated in red soil treated by selenite at levels of 0, 0.5, 1.0, and 5.0 mg Se kg^-1 in this study. The Se speciation in grains and the bioaccessible Se species were determined by the high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS), and the bioaccessibility of grain Se using an in-vitro simulation model was also analyzed. The results showed that Se in rice grains mainly existed in the organic forms, which accounted for more than 60% (61.7-69.6%) of the total Se but no significant differences were detected between the different treatments (P > 0.05). Concentrations of the glutelin-derived Se, as the dominated organic forms, were 116.4 ± 13.5, 243.3 ± 17.7, 579.7 ± 105.3, and 1904.0 ± 51.7 μg kg^-1, respectively under the soil Se treatments, accounting for 24.0%, 24.4%, 29.3%, and 30.7%, respectively of the total Se in grains, which was sightly increasing with the soil Se levels. The bioaccessibility of Se in grains were 54.3%, 51.1%, 57.0% and 68.1%, respectively for the Se treatments of 0.0, 0.5, 1.0 and 5.0 mg kg^-1. The speciation analysis results showed that selenomethionine (SeMet), as the main bioaccessible Se species, accounted for 31.6%, 40.0%, 40.4% and 58.2%, respectively, and the inorganic species, selenite, also accounted for approximately 10% of the total bioaccessible Se in grains. The gastrointestinal simulated results indicated that though the bioaccessible SeMet percentages in grains increased with the Se treatments and more than half of the grain Se could be bioaccessible for human beings, there was still a considerable amount of bioaccessible Se species needed to be identified. In conclusion, the application of selenite in soil can slightly increase the accumulation of glutelin-derived Se in rice grains and the bioaccessible SeMet, which are very important for human health. Additionally, for the Se-enriched rice cultivars, fractions of the organic Se in grain and the bioaccessible Se are still not very high. Thus, the transformation and migration of exogenous selenite in soil-plant system should be further studied, and next we will investigate the non-glutelin-derived Se in rice grains and identify those unknown bioaccessible Se species.