Abstract: Fermentation by yeast of corn straw at room temperature was tested. After completion of the fermentation, four nutrition indexes (CP, EE, CF and WSC) were tested and compared. When the ingredients of bran, yeast and corn straw were in the ratio 2∶2∶100, CP increased significantly by 1.93% after fermentation and EE by 0.51%. When the fermentation time was from 10-15 d, the increases were 6.49%-6.61% and 0.82%-0.95% respectively. The length of the corn straws had an obvious affect on fermentation. Fermentation was significantly increased by comminuting the straw, but this increased the cost of fermentation. If water content can be controlled within 60%-70%, the fermentation can be improved. Yeast fermentation had little effect on CF.