The invention discloses a high-density fermentation method of a heterogeneous-expression tetanus toxin receptor binding domain Hc (heavy-chain receptor C-terminal fragment). The method includes the steps of firstly, taking engineering bacteria containing tetanus toxin receptor binding domain Hc nucleotide sequences, and culturing until the OD600 value is 3.0-5.0 to obtain seed liquid; secondly, culturing the seed liquid in a fermentation culture medium until the dissolved oxygen value and pH rise fast, and supplementing materials when the rising amplitude of the pH is larger than 0.2/minute and the rising amplitude of the dissolved oxygen value is larger than 10%/minute; thirdly, performing induction expression when the OD600 value is 17, adding IPTG with the concentration being 0.2mM, cooling to 28 DEG C, continuing supplementing the materials, and culturing until the OD600 value is 40-50. The method has the advantages that the soluble tetanus toxin receptor binding domain Hc can be obtained in a high-expression manner, and the method is simple in fermentation process, low in cost, applicable to large-scale preparation of tetanus Hc subunit vaccines and promising in application prospect.