Rice glutelin is a multi-subunit storage protein and has high nutritional value. However, many glutelin subunits are still not identified by experiment approach. In this study, a novel subunit (OsGluBX) was discovered by sequence alignment in the UniProtKB database. And then, the OsGluBX of rice from japonica cv. Nipponbare and indica cv. 9311 were cloned and expressed in Escherichia coli system and further identified by Western blotting. The total storage proteins were extracted from the grains of Nipponbare and 9311, and the native OsGluBX were identified. The novel OsGluBX subunit was classified into the subfamily B based on its high homology to the subfamily B members and their immunoblotting identification against the subfamily-specific antibody. Furthermore, two-dimensional electrophoresis analysis showed similarity and difference of the entire glutelin profiles between the two subspecies. Moreover, the atomic coordinate of the OsGluBX was constructed based on homology modeling approach and refined by molecular dynamics simulations. The spatial conformation of the OsGluBX protein was stable during the simulation, and the obvious hydrogen bonds were observed to maintain the integrity and stability of the beta-sheets region of the OsGluBX. Research into this novel OsGluBX subunit has improved our understanding of the glutelin family in rice.