The objective of this paper was to investigate the effects of different protein feed on rumen fermentation and microbial community in vitro using 3 goats fitted with cannula. The four groups were plume meal group (group A), corn gluten meal group (group B), soybean meal group (group C) and fish meal group (group D), respectively. The PCR-SSCP technique was introduced to determine the microbial diversity. The results showed that the pH ranged from 5.80 to 6.80, and the lowest mean value was found in group C (6.19), while the highest occurred in group A (6.61). NH3-N concentration ranged from 36.8 to 120.1 mg/L, with group A recording the lowest average NH3-N concentration (54.9 mg/L), while group C (99.5 mg/L) writing the highest value. Microbial protein yields varied with groups (P<0.05 or P<0.01), and the lowest record was observed in group A (0.528 9 mg/mL), while the highest was found in group D (0.651 3 mg/mL). Group C showed the highest bacteria yield (0.330 9 mg/mL). Additionally, protein feed significantly affected the protozoa protein content/bacteria protein content (P<0.05 or P<0.01) and the lowest value was in group C (84.30%) and the highest value was in group A (107.00%). Further genetic fingerprint revealed that bacterial and protozoal profiles were subjected to substrates. In conclusion, protein stuff brought out the changes in ruminal microbial fermentation and flora, and fish meal had a better promoting effect on microbe growth.［Chinese Journal of Animal Nutrition, ２００9，２1（5）:673-679］