The purposes of this study are to elucidate the taxonomy and reproductive biology of Eptatretus chinensis. It includes three parts: (1) Description of external and internal taxonomic morphological characters. (2) Erection of hypothesis for the phylogenetic position of E. cheninsis using mtDNA 16S rRNA gene sequences. (3) Data on reproductive biology (male/female ratio, body length, monthly changes of eggs and spawn stage). Morphologically characters E. cheninsis and Paramyxine sheni are must similar to each other (number and distribution of slime pore in the brachial region and site of bifurcation of the ventral aorta). Sequences of the 16S rRNA indicate that E. cheninsis is more closely related to P. sheni, Quadratus nelsoni, Q. taiwanae, and Q. yangi than to its Eptatretus congeners including the sympatric E. burgeri, the eastern Pacific Ocean E. stoutii and the Oceania E. cirrhatus. Additionally, the sequence is most similar to that of P. sheni. 329 specimens were sampled during January to December, 2003. Relationship between body length and body weight is significant (P<0.001). There were more females than males in the samples. According to the occurrences of large eggs (i.e., diameter > 30mm) and egg sacs in the sampling period, it is suggested that E. chinensis spawned through out the year with a possible spawning peak in May to June. Small eggs (< 2 mm) were found in specimen as small as 232 mm. Diameters of eggs carried by a female was variable. The average numbers of large eggs was 28.5, and there was a negative relationship between egg number and egg diameter. Egg sacs (5-20mm), brown scars (1-4mm) and yellow spots (<1mm) were found on the mesenteric. Egg sacs were found in 307-461 mm females. The histological sections of the brown scar (20mm) and large egg sac (10mm), exhibited folding of membranous structures and the particles among the sac structures were similar. Therefore, it is suggested that the brown scar is a sympatric egg sac. The yellow spots and brown scars differed in their histological characters.