To evaluate the effect of the fence to Mongolian gazelles (Procapra gutturosa), we carried out the research on summer food habits of the Mongolian gazelles, using micro-histological analysis of the fresh feces, which were collected in Dalai Lake area of the Inner Mongolia, China and in the Eastern Province of Mongolia from July to August 2008. The results were as follows: (1）The vegetation coverage was (58.0±3.6)%, the aboveground biomass was (73.2±9.7)g/m2, the number of plant species was (17.5±3.5) in Dalai Lake area of the Inner Mongolia, China; The vegetation coverage was (68.2±5.0)%, the aboveground biomass was (76.1±6.9)g/m2, the number of plant species was (17.2±4.5) in the Eastern Province of Mongolia. Independent samples t-tests of the vegetation coverage, the aboveground biomass and the number of plant species were all non-significant between the two areas; We totally identified 18 plant families, 43 plant genus, 63 plant species in the two areas; (2) We collected 41 fresh fecal samples in Dalai Lake area and 37 fecal samples in the Eastern Province. Our results showed Mongolian gazelles in Dalai Lake area foraged on 10 plant families, 19 plant genus, 22 plant species, while living in Eastern Province of Mongolia foraged on 11 plant families, 24 plant genus,29 plant species; (3）The plants of the Gramineae were the main food of the Mongolian gazelles, occupied 791% and 73.2% of their diets respectively in the Dalai Lake area and the Eastern Province. The percentage of the Leguminosae foraged by Mongolian gazelles in the Eastern Province (10.0%) was higher than that in Dalai Lake area (30%). The percentage of the Chenopodiaceae foraged by Mongolian gazelles in Eastern Province was 2.7%, however, in Dalai Lake area, Chenopodiaceae was not foraged. There are 3 same plants species in the top 5 of the plants foraged by Mongolian gazelles by the proportion between the two areas. The proportion of Leymus chinensis and Stipa sp., Gramineae, were the main feeding species, occupied 63.6% and 57.7% respectively in the two areas; Eragrostis Beauv was the third in the food composition of the Mongolian gazelles in Dalai Lake area (5.8%), while 0.2% in Eastern Province. Medicago falcata Leguminosae was the fourth in the food composition of the Mongolian gazelles in Eastern Province (6.8%), as well as the species was not foraged in Dalai Lake area；(4) The niche breadth (Bj) of Mongolian gazelles’ summer food composition in Dalai Lake area was 2.0 and that in the Eastern Province was 2.3; (5) The index of percent similarity (PS) of Mongolian gazelles′ summer diets was 0.7 between the two areas; (6) the major food rank was significantly correlated between the two areas, and the Spearman′s correlation coefficient reached 0.6 (p < 0.05). We concluded that though the Mongolian gazelles in Dalai Lake area were mainly restricted to limited grassland by the fence, the food composition was still significantly similar to that of Eastern Province of Mongolia. Ours research showed that the habitat restriction had no significant effect on the summer food habits of the Mongolian gazelles.