Abstract: In the article,the comparative study of the bioactivity was carried out between eight yeast strains and four mold strains to screen good strain with high activity.The biomass,the crude protein content,living bacteria number,fermentative fragrance of eight yeast strains were determined,and the biomass and synthesis of the enzymes of four mold strain was measured.The result indicated that yeast of Saccharomyces cerevisiae BC,BD,Candida utilis BY,Candida tropicalis BR and Aspergillus niger H3 had the excellent production performance,which can be selected as experimental strains of probiotics for ruminants.