Probiotics have many effects such as antihypertensive, prevention of cancer, antioxidation, reduction of dermatitis symptoms, improvement of mineral absorption, reduction of allergic symptoms, and decrease of cholesterol, However, the main role of probiotics is that they balance intestinal microbials proportion. L. acidophilus is one of probiotics and microflora in intestine. It has an acidification activity, aroma production, texture formation and probiotics properties. We studied on the roles of L. acidophilus in mice. In this study, body weights of mice were decreased when administration of L. acidophilus ($1{ imes}10^{10}$ CFU) and swimming ability has been raised than a normal group after feeding on L. acidophilus ($1{ imes}10^{10}$ CFU). After taking L. acidophilus ($1{ imes}10^{10}$ CFU), total white cells were increased than a normal group; hemoglobin and thrombocytes were increased. The level of cholesterol and triglyceride were decreased in blood analysis. We knew L. acidophilus is related to innate immune system. We found out the secretion of cationic peptide was increased in the Lysoplate assays as a result of L. acidophilus ($1{ imes}10^{10}$ CFU) administration. Appearance rate of lysozyme was also increased than the normal group on an immunohistochemistry stain. We confirmed L. acidophilus contributes to host health through innate immune system stimulation. L. acidophilus more than $1{ imes}10^{10}$ CFU are thought to be beneficial for the host health and prevention of intestinal diseases in field condition.