This study aimed to evaluate the effects of starter feeds of different physical forms on rumen fermentation and microbial composition for lambs. Twenty-four eight-day-old male Hu lambs (5.04 ± 0.75 kg body weight) were fed either milk replacer (MR) and pelleted starter feed (PS), or MR and textured starter feed (TS) in pre-weaning (day 8 to 35) and post-weaning (day 36 to 42) lambs. And the MR was fed by bottles to lambs at 2% of body weight at day 8 divided as three equal amounts at 08:00, 14:00 and 20:00 in pre-weaning. And the lambs were readily availed starter feeds and clean fresh water in the whole experiment. Six lambs for each treatment were euthanized at day 21 or 42 for sampling. The results showed the total volatile fatty acids, propionate and butyrate of rumen liquid in TS groups were all higher than them in PS groups respectively for pre-weaning and post-weaning lambs (P<0.05), and the pH of rumen liquid in TS group was lower than it in PS group for post-weaning lambs (P<0.05) . Moreover, the pH of rumen and OTUs in TS group had trends to lower than them in PS group for pre-weaned lambs (P = 0.061, P = 0.066). TS established the predominant Phylum, Bacteroidetes, earlier than PS, and increased significantly the relative abundances of Sharpea compared to PS at level of genus (P<0.05) for pre-weaning and post-weaning lambs. TS were more benefits to trigger rumen development for lambs.