A fibroblast line was successfully established from Mongolian horse ear marginal tissue by using a primary explant technique and cell cryogenic preservation technology. Biological analysis showed the following: The cells were adherent and exhibited density-dependent inhibition of proliferation; assays of microbial contamination from bacteria, fungi, and mycoplasma were negative; the population doubling time of the cells was 33.9 h; and a 2n chromosome number of 64 at a frequency higher than 80%. A lack of cross-contamination of this cell line with other species was confirmed by isoenzyme analysis of lactic and malic dehydrogenases. In order to study exogenous gene expression, four fluorescent proteins, pEGFP-N3, pEGFP-C1, pDsRed1-N1, and pEYFP-N1, were transfected into the cells. The corresponding fluorescence was distributed throughout the cytoplasm and nucleus 12 h after transfection. This cell line not only preserves the genetic resources of the Mongolian horse at the cellular level but also provides valuable materials for genomic, postgenomic, and somacloning research in this species.