Abstract： Objective:A subunit vaccine against SARS-CoV-2 BA.2 variant was prepared by prokaryotic expression system and its immunogenicity was evaluated.Methods:The recombinant plasmid of BA.2 variant RBD and the tandem of RBD and TT-P2 epitopes was constructed by molecular cloning technology, and recombinant proteins So and Sot were obtained by protein purification technology. Mice were immunized by intramuscular injection after mixing protein So/Sot as immunogens with Al(OH) 3 adjuvant to evaluate the effect of cellular and humoral immunity. Results:High purity soluble protein were obtained by dialysis and renaturation after expressed by prokaryotic system. The number of antigen-specific T lymphocytes secreting IFN-γ and IL-4 (213.7±0.6 and 311.7±1.5) in the Sot group induced by mice was significantly higher than that in the So group (94.3±16.8 and 185.7±4.2) ( P<0.001). The serum antibody level induced by Sot group was higher than that in the So group, the geometric mean titer (GMT) of neutralizing antibodies against BA.2 strain were 588 and 337, respectively ( P<0.05). Sot protein induced Th1/Th2 mixed type immune response with the predominance of Th2 type. Conclusions:The protein subunit vaccine expressed by the prokaryotic system have excellent cellular and humoral immunogenicity, which provides a strong theoretical basis for the development of the protein subunit vaccines of the SARS-CoV-2 Omicron variant.