The histological structures of the dorsal-ventral skin in three species of genus Rana, Plateau Brown Frog (R. kukunoris), Chaochiao Brown Frog (R. chaochiaoensis) and Omei Brown Frog (R. omeimontis) were observed using paraffin section and hematoxylin-eosin staining. A paired t-test was used to analyse differences in thickness of skin, relative number of mucous glands and transverse areas of a mucous gland between dorsal and ventral skin in each species. Differences in thickness of skin and transverse areas of a mucous gland among species were tested using One-way ANOVA. We used Mann-Whitney U-test to compare differences in relative number of mucous glands and transverse areas of a granular gland among species, because normal distribution of the variance was not met. All statistical tests were performed using software SPSS 13.0. All values given were shown as Mean ± SD. The adaptive mechanism of skin to terrestrial environment was also discussed. The results show that the skin structures of 3 frog species studied are similar, composed of epidermis and dermis (PlateⅠ). The epidermis is keratinized stratified squamous epithelium, which is made up of stratum comeum, stratum granusum, stratum spinpsum and stratum germinativum. The dermis consists of two layers, the stratum spongiosum and the stratum compactum. The stratum spongiosum is mostly composed of loose connective tissue. The stratum compactum is made up of dense connective tissue. The collagen fibers in the stratum compactum lie in bundles parallel to the body surface. There are three types of cutaneous glands, mucous glands, granular glands and lipidic glands in the stratum spongiosum (PlateⅠ). The mucous glands are evenly distributed in the dorsal-ventral skin, however, the granular glands mostly are distributed in the dorsal skin in a cluster. A new type of eosinophil gland (Plate Ⅰ: 5, 8), different from mucous glands and granular glands described before, have been found in R. kukunoris. The skin thickness varies both between different species and between different regions of skin from the same animal (Table 1), and it is related to the size of mucous glands (Table 2). In R. kukunoris, the epidermis contains a few capillaries and rich chromatophores, and rich cutaneous glands exist in the stratum spongiosum, which is probably a strategy of adaption to environment with high altitude, low temperature, and strong ultraviolet radiation. The calcified layer lies between the stratum spongiosum and the stratum compacturn in R. chaochiaoensis and in R. omeimontis (PlateⅠ: 2﹣4, 10). It is a wavy strip and stains blue by hematoxylin-eosin staining. The calcified layer is more developed in the dorsal skin than in the ventral. Its function may be associated with hydric balance, calcium storage, or serve as a barrier in the exchange of substances.