Abstract: Abstract: Using Kluyveromyces marxianus M3 isolated from Tibetan Kefir to study tolerance characteristics of the gastrointestinal tract and cholesterol-lowering effects in vitro. Viable count was used to detect M3 stains’ tolerance characteristics of the gastrointestinal tract separately under simulated gastrointestinal tract environment pH1.5~4.5, salt concentration 0.3~3.0%, sodium chloride 3.0~6.0%.At the same time, using O-phthalaldehyde to detect the effect of its cholesterol-lowering. The result shows that after 4 hours under pH1.5~4.5 the viable can get 106cfu/mlunder.The viable can be 105~106cfu/ml under 0.3%~3.0% bovine bile salt and 3.0%~6.0% sodium chloride(8h).Also, in the simulated gastrointestinal tract environment pH1.5~3.0(4h), salt concentration 0.3~3.0%(8h) the cholesterol-lowering can reach 60%. M3 strains have strong tolerance characteristics against the environment of the gastrointestinal tract and the good cholesterol-lowering ability, which provide the experimental basis for the development of cholesterol-lowering functional foods and probiotics’ study.