Yield improvement is an important goal in maize breeding. Grain size and weight are two main yield components in cereal crops. In this study, 3’-RACE and RT-PCR were employed to isolate the maize orthologous gene according to the sequence information of the OsGW2 gene that was reported to be a major QTL controlling rice grain width and weight by encoding a RING-type protein with E3 ubiquitin ligase activity. The sequence and expression pattern of the maize target gene were analyzed. The results indicated that the coding sequence of the isolated maize orthologous gene has 1287 bp and encodes 428 amino acid residues. Blastx function analysis revealed that the maize orthologous gene encodes E3 ubiquitin protein enzyme. Compared to the complete coding sequence (CDS) of OsGW2, the homologous gene showed an 83% of similarity to OsGW2. We temporarily designated this homologous gene as ZmGW2-1. Meanwhile, ZmGW2-1 highly expressed in maize ears, indicating that it might play important roles in maize ear development. Isolation of ZmGW2-1 laid a good foundation for further study on its functions.