Abstract: This experiment aims to establish a high-density fermentation process for Haemophilus parasuis. By comparing the culture effect of TSB, BHI, and LB medium, the TSB medium was selected for further optimization, and the optimized medium was used to carry out high-density fermentation culture of Haemophilus parasuis in a 10 L fermentation tank. The results showed that the number of viable bacteria of serum type 4 JS strain was 2.5×10^10 CFU/mL, and that of serum type 5 ZJ strain was 2.5×10^10 CFU/mL, and the addition of serum was reduced by half through the combination use of batch -supplementation and fed batch culture. Three consecutive batches of fermentation experiments at the 1 000 L fermentation scale identified that the process could be used for large-scale production of inactivated vaccine antigens of Haemophilus parasuis. In addition, animal experiments were carried out on three batches of fermentation antigens using replacement animal of guinea pigs, and the results showed that the antigens were all qualified. In summary, our results provide a theoretical basis for the large-scale production of bivalent inactivated vaccines of serum type 4 and type 5 of Haemophilus parasuis.