A Streptococcus suis (S. suis) vaccine is provided. For the S. suis vaccine, an antigen is a protein with an amino acid sequence shown in SEQ ID NO: 2. A preparation method of the S. suis vaccine is provided, including the following steps: mixing a white oil and aluminum stearate to obtain a white oil adjuvant; adding poly sorbate 80 to an aqueous solution of the protein with the amino acid sequence shown in SEQ ID NO: 2, and thoroughly mixing to obtain an antigen solution; and mixing the antigen solution with the white oil adjuvant according to a volume ratio of (0.5-1.5):2, and emulsifying to obtain the S. suis vaccine. An animal immunized with the S. suis vaccine of the present disclosure can effectively resist the attack of S. suis serotype 2, 3, and 31, with a vaccine protection rate as high as 100%.