Abstract: In this study, the law of acidification of dry rice straw, turf grass, dry corn straw and fresh corn straw in cow dung liquid was investigated. The property change of digestive solution during digestion process was evaluated, the rate of weight loss and soluble chemical oxygen demand (sCOD) change were used to analyze the efficiency of raw materials degradation and acidified product respectively. The results indicated that the degradation effects of four kinds of lignocelluloses materials in cow dung liquid were obvious, while the processes were different. The total weight loss of turf grass was the fastest and most with 73.25%; The weight loss of dry rice straw was 50%, close to that of turf grass with total loss of 72.01% on the 10th day; The weight loss of fresh corn straw was also close to that of turf grass and dry rice straw, which reached up to 68.36% on the 18th day and 71.64% by the end; The dry corn straw had the smallest weight loss of 57.6%. The decomposition rate of lignocelluloses of four kinds of materials were in order of rice >turf grass>fresh con straw>dry corn straw, and the hemicelluloses decomposition rates were best of all, cellulose and lignin were followed. The volatile fat acids produced by fresh or dry corn straw were more than that of rice straw and turf grass, the maximum total VFA of rice straw, turf grass, fresh corn straw and dry corn straw were in order of 3.91, 0.54, 7.16 and 10.99 g/L. The accumulation of acidification product was achieved from dry rice straw and turf grass, which was favorable, but the dry or fresh corn straw were unfavorable.