Probiotic feed yeasts were made from the raw materials of defatted soy meal, rice hull and corn straw by solid state fermentation. The culture medium ingredients were optimized by the orthogonal experiment. The model of fermentative condition was developed by the simplex-centrioid mixture design and analyzed by the response surface analysis．The results were as follows: defatted soymeal∶rice hull∶corn straw was in the ratio 5∶2∶2. Forty grams of the raw materials were added with 4 grams of glucose，0.2 grams of （NH₄）₂SO₄ and 1× mono-microelement combination. The inoculum volum was 3.5%. The culture thickness was 1.3 cm. The ratio of water addition to raw materials was 1∶1(m/m). The fermentation temperature was 30.6 ℃ and the fermentation period was 28 h. Under the above conditions, living yeast cells was obtained at （2.92±0.05）×10⁹ CFU/g.