A short-chain peptide capable of controlling spermatozoa fertilization performance is supplied in an in vitro culture medium of spermatozoa and oocytes to increase the success rates of in vitro fertilization. The short-chain peptide comprises an amino acid sequence H-Tyr-Asn-Trp-Asn-Ser-Phe-Gly-Leu-Arg-X-NH2 (SEQ ID NO: 1), where X denotes Tyr or Phe, and the sequence ends with an amide. The short-chain peptide is conducive to adjustment of the concentration of free calcium ions inside the cells of the spermatozoa and thus enhancement of the success rates of in vitro fertilization.
