Objective:　Studying　the　lyophilization　protective　capacity　of　antifreeze　polypeptide　on　Streptococcus　thermophilus　and　investigating　its　relative　mechanism.　Method:　Detecting　the　cell　viability　of　Streptococcus　thermophilus　via　the　OD　method　after　lyophilization.　Antifreeze　polypeptide　of　different　mass　concentration　was　added　to　Streptococcus　thermophilus,　and　then　the　cell　viability　of　Streptococcus　thermophilus　after　lyophilization　was　detected.　Conclusion:　Antifreeze　polypeptide　was　proved　to　reduce　the　lyophilization　damage　on　Streptococcus　thermophilus.　Comparing　the　final　cell　viability　of　different　groups,　the　best　mass　concentration　of　antifreeze　polypeptide　was　1　mg/mL,　and　the　optimum　pH　was　8.0.　Under　the　condition,　the　cell　viability　of　antifreeze　peptide　treatment　group　was　significant　higher　than　control　group.　Under　the　investigation　of　scanning　electron　microscopy　(SEM),　cells　of　treatment　group　were　full　and　integral;　while　cells　of　control　group　were　just　shrinking,　which　visually　showed　the　protective　ability　of　AFP　on　the　cells.　©　2018,　Editorial　Office　of　Journal　of　CIFST.　All　right　reserved.