Abstract: Objective: To efficacies of the different immunization approaches in preparation of Streptococcus mutans serotype C antiserum in rabbits.Methods: Heat-killed cells and live cells of Streptococcus mutans serotype C STCC25175 were injected into the ear vein of 30 rabbits in different sequences.The antibody titer and death condition of the rabbits were observed.Results: Both the immunization by injecting live cells and immunization by injecting firstly death cells and then fresh live cells produced titers 1:32 in the 27th-30th day.Injecting live cells caused a high death rate of rabbits while injecting firstly death cells then fresh live cells caused no death.Conclusions: Immunization by injecting firstly death cells then fresh live cells is a good sequence to get Streptococcus mutans antiserum.