This experiment was conducted to evaluate the nutritive value of different feeds by in vitro ruminal fermentation method. Experiment 1 was used to compare the in vitro fermentation characteristics of different forages (wheat husk, Chinese wildrye hay, rice straw, high-energy forage, American alfalfa, Chinese alfalfa, whole-plant corn silage, peanut vine silage, corn straw silage and hybrid sorghum silage), experiment 2 was used to compare the in vitro fermentation characteristics of different protein feeds (soybean meal, cottonseed meal, rapeseed meal, sesame meal and palm meal), and experiment 3 was used to compare the in vitro fermentation characteristics of different feed combinations (rice straw combination, alfalfa combination, Chinese wildrye hay combination and wheat husk combination, and the concentrate in those combinations was the same). The results showed as follows: after 48 h in vitro fermentation, the corn silages (including whole-plant corn silage and corn straw silage) and alfalfas (including American alfalfa and Chinese alfalfa) had higher gas production (GP), dry matter degradability (DMD) and total volatile fatty acid (TVFA) concentration compared with other forages (P<0.05), while the GP and DMD of wheat husk were significantly lower than those of other forages (P<0.05). After 48 h in vitro fermentation, soybean meal had the highest GP and the fastest fermentation rate. There were greater differences in organic matter degradability (OMD) and DMD among different protein feeds, and the OMD and DMD of soybean meal were the highest and significantly higher than those of other protein feeds (P<0.05); the microbial crude protein (MCP) concentration of soybean meal was also the highest and significantly higher than that of sesame meal and palm meal (P<0.05). For different feed combinations, the smaller neutral detergent fiber/crude protein (NDF/CP), the faster fermentation rate, and the higher degradability. The correlation analysis showed that the NDF/CP was negatively correlated to DMD (P<0.05). These results suggest that, 1) for forages, corn silages and alfalfas have the higher GP and faster fermentation rate, while the wheat husk has the lower GP and the slower fermentation rate; 2) for protein feeds, the GP, fermentation rate and MCP concentration of soybean meal are higher than those of other protein feeds; 3) for feed combinations, NDF/CP affect the in vitro fermentation characteristics of feeds, which is manifested as the smaller NDF/CP, the shorter fermentation lag phase, the faster fermentation rate, and the higher degradability.