72% whole amaranth and 28% rape straw were mixed serving as raw materials with eight treatments including molasses group, lactic acid bacteria group, cellulose complex enzyme, molasses with lactic acid bacteria group, molasses with ellulose complex enzyme group, lactic acid bacteria with cellulose complex enzyme, molasses with lactic acid bacteria with cellulose complex enzyme group and only water as a blank control group. The sample were subject to fermentation for 30 d and then to analysis. The results showed as follows: compared with control group and without molasses groups, the PH, acetic acid content, washing fiber content in molasses groups significantly decreased(P<0.05), and V-Score, crude protein content, water-soluble carbohydrate content and relative feed value in molasses groups also significantly increased in the mixed silage of amaranth and rape straw(P<0.05). Mixed silage quality of amaranth and rape straw could be significantly improved by adding molasses.