In order to study the effects of two different feeding methods, grazing and feeding, on the rumen fungal flora of Tan sheep, this experiment adopted a randomized block design and selected the newborn grazing Tan sheep with close weight and health. There were 12 lambs in each group. The lambs in the grazing group were reared with grazing lactating ewes. The rearing group was kept with the rearing ewes. At the age of 2 months, the lambs were slaughtered and analyzed the fungal flora structure in the rumen fluid by interstitial (ITS) rDNA hypervariable region sequencing. The results showed as follows:the diversity of fungi in the rumen fluid of the lambs in the grazing group was significantly higher than that in the rearing group (P<0.01). Six phyla were identified in the rumen fungal flora in the grazing group and the rearing group, including 5 phyla in the rearing group and 1 phylum in the grazing group. The relative abundance of Neocallimastigomycota in the rumen the grazing group was significantly higher than that in the rearing group (P<0.01); the relative abundance of Ascomycota in the rearing group was significantly higher than that in the grazing group (P<0.01). The dominant phylum in the rumen fluid in the grazing group were Ascomycota and Neocallimastigomycota, and the dominant phylum in the rearing group was Ascomycota. A total of 69 genuses were identified from the rumen fungal flora in the grazing group and the rearing group, including 55 genuses in the grazing group and 56 genuses in the rearing group. The relative abundances of Kazachstania, Gibberella and Saccharomyces in the rearing group were significantly higher than those in the grazing group (P<0.01), and the relative abundance of Lepista was significantly higher than that in the grazing group (P<0.05). The relative abundances of Piromyces, Caecomyces, Neocallimastix, Neocallimastigaceae_NA and Chalastospora in the grazing group were significantly higher than those in the rearing group (P<0.01). The relative abundance of Pichiaceae_NA was significantly higher than that in the rearing group (P<0.05). The dominant genus in the grazing group was Kazachstania and Piromyces, and the dominant genus in the rearing group was Kazachstania. It is concluded that feeding methods has a significant impact on the construction of rumen fungal flora in 2-month-old Tan sheep.