Seasonal variations in distribution and biological characteristics of snailfish Liparis tanakae in the central and southern Yellow Sea were examined based on the bottom trawl survey data in July-August, October, 2009 and January, May 2010. The results showed that the average body length and the body weight markedly increased from spring (4.7 cm, 3.3 g) to winter (34.2 cm, 764.9 g). The average body length of male individuals was significantly larger than that of female individuals in summer and autumn (P<0.05), and in winter (P<0.01), but there was no significant difference between males and females in spring (P>0.05). By the analysis of covariance, there was a marked difference in growth between male and female individuals in autumn, but there were no significant differences in other seasons. T-tests showed that allometric factor b was lower than 3 in spring and winter (P<0.05) and larger than 3 in summer (P<0.05). Sex ratios (♀∶♂) changed with seasons and body length; larger body length corresponded with higher proportion of male individuals, whereas smaller body length corresponded with higher proportion of female individuals. The proportion of male individuals was higher in summer (0.70∶1, P<0.05) and lower in autumn (1.35∶1, P<0.05). However, there was no significant difference in sex ratios in winter and spring. The rate of sexual maturity reached 41.3% in winter, but was almost zero in other seasons of the year. The empty stomach rates were low (0-1.73%) in all seasons. The average feeding intensity was larger than class 2.5 through the whole year and showed significant gender differences in the spawning season (male>female, P<0.05), but the condition factors of male individuals were at the lowest level (1.52). The relative biomass and the proportion of snailfish catch in the total catch increased from spring (0.17 kg/h, 1.54%) to autumn (15.36 kg/h, 33.05%) and decreased in winter (2.37 kg/h, 5.60%). In the present study, the relative biomass (kg/h) and the proportion of snailfish catch in the total catch in summer and autumn were much larger than those in summer and autumn, 2000. The snailfish is mostly found in sea areas with temperature 7.8-13.6°C and salinity 3.20%-3.38%, which indicates that it could be a low temperature and high salinity species. Its average body weight was significantly related to water depth (excluding in autumn). For example, bigger size individuals inhabited deep water in spring and shallow water in summer and winter. However, most snailfish were found in deep water (>65 m) throughout the year, except in spring. These suggested that the distribution of snailfish in spring (juvenile stage) was also affected by diet species, and individuals with body length between 2.2 cm and 5.7 cm appeared in areas of high-density plankton and Gammaridae species in the southern Yellow Sea, whereas those with body length between 5.8 cm and 17.0 cm were distributed in sea areas with high abundance of the shrimp Crangon affinis in Haizhou Bay. In addition, snailfish males might perform parental care. According to the combined information on the distribution of mature and juvenile snailfish, the deep-water area of the central Yellow Sea might represent the spawning ground for snailfish in addition to Haizhou Bay.