The objective of this study was to assess the effect of dietary probiotics on rumen fermentation and the bacterial community in dairy calves. Twelve Holstein calves were randomly allocated to three treatments: a basal diet, the basal diet supplemented with Lactobacillus plantarum GF103 (LB) or basal diet supplemented with a mixture of Lactobacillus plantarum GF103 and Bacillus subtilis B27 (LBS). A milk replacer was fed to calves from 8days of age. A starter and alfalfa hay was offered ad libitum from 21 and 28days of age, respectively, and the orts were weighted daily. The ruminal fluid was sampled at 56 and 83days of age to determine the rumen fermentation characteristics. The bacterial community was analyzed by denaturing gradient gel electrophoresis (DGGE) and the number of certain bacteria was quantified by real-time polymerase chain reaction. The ratio of total dry matter intake to average body wieght was higher in the control (P<0.05). The DGGE fingerprint of the 16S ribosomal RNA gene was affected by the blended probiotics at 83days of age. The number of Ruminococcus albus was lower in the LB and LBS treatment (P<0.05). Oral administration of the probiotics affected the rumen bacterial community and the numbers of cellulolytic bacteria decreased.