Sea cucumbers (Stichopus japonicus) belonging to the phylum Echinodermata are traditional tonic consumed by Chinese and Japanese. The major edible parts of sea cucumber are the body wall mainly consisting of collagen and mucopolysaccharides. More than 21 types of collagen have so far been identified in various tissues and their roles have been investigated. In invertebrate, at least 2 types of collagen, type Ⅰ and type Ⅴ are found to exist. There is little information about the collagen of sea cucumber except for few reports on S. japonicus and Cucumaria frondosa, respectively. However, results of the former findings were not consistent with that of the latter about the molecular composition of the sea cucumber collagen. In this paper, the intact collagens were isolated from the body wall of S. japonicus by a new method and their physical and chemical characterization were studied. The results showed that pepsinsolubilized collagens(PSC) without telopeptide could be prepared at low temperature. Through the ultraviolet scanning spectra from 190 to 400 nm, the PSC presented maximum absorption at 220 nm which was consistent with that of type Ⅰcollagen. The compositional features of the amino acid were with the high contents of glycine(329 residues/1000) and hydroxyproline(66 residues/1000), but with low contents of tyrosine, phenylalanine and histidine. No cysteine was detected. The ratio of hydroxyproline to proline was 0.69. It was conc luded that PSC was typical type Ⅰcollagen. This was the first report about the thermal stability temperature (T^s) of sea cucumber collagen which was 57 ℃ as measured by DSC, about 5 ℃ lower than that of type Ⅰcollagen of calf. The content of total polysaccharide determined with phenol sulfuric acid method was 0.61％ and the glycosaminoglycan measured with cationic dye of methylene blue was 0.48％. The collagen could be separated from glycosaminoglycan by DEAE52. Based on SDS polyacrylamide gel electrophoresis(SDSPAGE), the purities of PSC were higher. Judging from their electrophoretic patterns, PSC contained β, α and a few γ chains, while α chain resembled α¹ chain of typeⅠcollagen of vertebrate, however, the presence of （α^{1）3 trimers was evident.}