Abstract: The aims of the present study were to investigate the immune enhancement effect and production performance of Yeast Polysaccharide (YPS) on rats. The results showed that each index in YPS groups was higher than that in blank control group. Any dose of YPS by orally administrated significantly raised spleen and thymus index, serum IgA, IgG, AKP and LZM level, phagocytic index and phagocytic activity of macrophages in the rats. Meanwhile it can increase production performance of rats. Results suggested that any dose of YPS can enhance immunologic function and production performance of rats and the dose of 100 mg kg-1 has the most obvious efficacy.