Most of the currently licensed viral and bacterial vaccines produced in the world are in state of antigen suspension and the immunogenicity of vaccines could be maintained for one or two years only by keeping in the refrigerator, but without refrigeration vaccines would easily lose their immunogenicites. In this study, as a step to develope the method of increasing the stability of vaccines and maintaining the immunogenicity of vaccines for a long time at room temperature or higher temperature, trehalose, glucose and lactose at different concentration were added into the Hantaan virus vaccines and then kept at $37^{circ}C$ for 12, 24, 48 hours and at room temperature for seven days respectively. Treated vaccines were then inoculated respectively into ICR mice and the titers of antibody against the antigen of Hantaan virus from the mice sera were evaluated. Vaccine without sugar lost immunogenicity completely in 24 hour at $37^{circ}C$, but the vaccines containing trehalose could maintain some of the immunogenicity even after exposure at $37^{circ}C$ for 48 hours and the best concentration of trehalose for maintaining the immunogenicities of vaccines was $7.5{sim}10$ percent. The results suggest that addition of trehalose could increase the stability of Hantaan virus vaccine.