Objective To analyze ORF3a protein in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by bioinformatics. Methods Amino acid sequence of ORF3a was obtained from UniProt. Physicochemical properties of the protein were analyzed by ProtParam tool. Secondary and tertiary structures were predicted by SOPMA and SWISS-MODEL. Hydrophobicity, signal peptide, and transmembrane region of ORF3a protein were analyzed by PortScale, Signal IP 4.0 Server, and TMHMM Server 2.0. B cell and T cell surface epitopes as well as phosphorylation sites were predicted by ABCpred, SYFPEITHI and NetPHos 3.1 Server. Antigenicity and allergenicity were predicted by VaxiJenv 2.0 and AlgPred server. Results ORF3a is a stable, hydrophobic protein with 3 transmembrane helical regions and 29 phosphorylation sites. It contains 275 amino acids and multiple T and B cell epitopes, and is antigenic and non-allergenic. Conclusion ORF3a protein is structurally stable. It contains multiple T and B cell epitopes, thus can provide basis for the study of SARS-CoV-2 multi-epitope vaccines.