The　original　L.　acidophilus　strain　FZU-LA1301　was　treated　with　UV　mutation　and　high　temperature　acclimation.　After　a　series　of　UV　mutation　and　high　temperature　acclimation　treatment,　a　thermo　tolerant　strain　FZU-　LA1301X　was　developed.　The　results　indicated　that,　after　mutation　and　acclimation,　temperature　tolerance　was　increased　from　37　to　45　.　The　stationary　phase　of　the　strain　appeared　at　15　h,　which　was　shorten　from　24　h.　In　anaerobic　environment,　the　viable　number　reached　8.24　lg　CFU/mL　during　stationary　phase.　After　mutation　and　acclimation,　there　was　no　significant　change　in　pH　value　of　the　fermentation　broth,　which　were　both　around　4.0.　After　freeze　drying,　the　strain　FZU-LA1301　and　FZU-LA1301X　were　kept　in　room　temperature.　The　viable　counts　of　strain　FZU-LA1301　decreased　1　log　value　in　1-2　days,　while　the　strain　FZU-LA1301X　can　keep　5-6　days.　So　the　strain　FZU-LA1301X　more　stable　than　original　strain　in　room　temperature.　The　mutant　stain　had　a　certain　tolerance　ability　of　pepsin,　trypsin　and　bile　salts.　The　strain　FZU-　LA1301X　obtained　in　this　study　has　better　heat　resistance,　and　the　microbial　feed　additives　fermented　with　this　strain　had　more　stable　in　room　temperature,　which　may　substitute　the　traditional　acidifying　agent.　©　2018,　Editorial　Office　of　Journal　of　CIFST.　All　right　reserved.