The dorsolateral fold is an important morphological structure of Anurans, but little is known about its histological structure and function. We studied the histology and histochemistry of the dorsolateral fold and dorsal skin by using Hematoxylin-Eosin, Alcian Blue-Periodic Acid Schiff and Masson staining methods in four Ranid species: Dianrana pleuraden, Sylvirana latouchii, Nidirana daunchina and Boulengerana guentheri. Our results found that: 1) The skin gland units of Ranidae consist of rich and diversified mucous and granular glands. There were two types of ordinary mucous glands (OMGs), types OMGⅠand Ⅱ, and the former was absent in B. guentheri and N. daunchina (Fig. 1 b2, d2). The granular glands were categorized into typeⅠ, type Ⅱ and specialized type, but type Ⅱ was only found in N. daunchina (Fig. 1 b3, Fig 2 b3). Specialized granular glands were only found in the dorsolateral fold of S. latouchii and B. guentheri (Fig. 2 c3, d3). 2) The dorsolateral fold consists of a fat layer which is similar between D. pleuraden and N. daunchina (Table 1, Fig. 2 a3, b3). The dorsal skin of N. daunchina had a fat layer whereas this layer was absent in D. pleuraden. The fat layer was 1.52 times and 1.60 times thick as their dermis in D. pleuraden and N. daunchina, respectively. The dorsolateral fold contained a layer of clustered and enlarged specialized granular glands in the dermis which was similar in S. latouchii and B. guentheri (Table 1, Fig. 2 c3, d3). Two types of granule secretions were found in the specialized granular gland (Fig. 2 d3). 3) Their functions included energy storage and antipredation. We speculate that the structural and functional evolution of the dorsolateral fold is related to environmental adaptation. The evolution of two types of dorsolateral fold in ranid species may represent two evolutionary orientations.