This experiment was conducted to compare the nutrient apparent digestibility of sugarcane by-products by endogenous indicator method combining with substitution method. Thirty-six 1-year-old Simmental bulls with body weight of about 350 kg were selected and divided into 6 groups with 6 replicates in each group and 1 cattle in each replicate. Test 1:the experimental design was for determining the nutrient apparent digestibility of sugarcane tops silage, which was divided into test Ⅰ phase and test Ⅱ phase, In the test Ⅰ phase, group 1 was fed a total mixed ration (TMR) which was used elephant grassy as roughage, and group 2 was fed a TMR which used 30% (dry matter basis) sugarcane tops silage instead of elephant grass; in the test Ⅱ phase, group 1 was fed a TMR which used 30% (dry matter basis) sugarcane tops silage instead of elephant grass, and group 2 was fed a TMR which was used elephant grassy as roughage. Each phase lasted for 14 days, including 9 days of pre-test period and 5 days of test period, and the total test period was 28 days. The alkalized sugarcane bagasse (test 2) and steam explosion sugarcane bagasse (test 3) were designed to be the same as the sugarcane tops silage. The results showed that the dry matter apparent digestibility of sugarcane tops silage, alkalized sugarcane bagasse and steam explosion sugarcane bagasse was 83.18%, 59.74% and 62.22%, respectively; the organic matter apparent digestibility was 74.74%, 58.96% and 61.56%, respectively; the gross energy apparent digestibility was 70.98%, 59.61% and 62.72%, respectively; the crude protein apparent digestibility was 66.93%, 12.16% and 15.69%, respectively; the neutral detergent fiber apparent digestibility was 47.47%, 32.65% and 38.28%, respectively; the acid detergent fiber apparent digestibility was 33.77%, 25.70% and 22.04%, respectively; the digestible crude protein content was 5.21%, 0.21% and 0.33%, respectively; and the digestible energy was 12.78, 10.14 and 10.76 MJ/kg, respectively. The apparent digestibility of dry matter, organic matter, crude protein, neutral detergent fiber, acid detergent fiber and gross energy of sugarcane tops silage was significantly higher than that of alkalized sugarcane bagasse and steam explosion sugarcane bagasse (P<0.05), the apparent digestibility of crude protein and neutral detergent fiber of steam explosion sugarcane bagasse was significantly higher than that of alkalized sugarcane bagasse (P<0.05), the apparent digestibility of acid detergent fiber of steam explosion sugarcane bagasse was significantly lower than that of alkalized sugarcane bagasse (P<0.05). Based on the above results, among the 3 kinds of sugarcane by-products, the sugarcane top silages have the highest feeding value, and the steam explosion sugarcane bagasse is better than alkalized sugarcane bagasse.