Research on basic biology of yellow-fin tuna Thunnus albacares is essential for its stock assessment. In this paper, some biological characteristics of T. albacares were preliminarily studied based on the long-line catches in the South Pacific Ocean near Solomon Islands from August to October 2010. The results are shown as follows: (1) The fork length (FL) ranged from 47.5 to 166.5cm with an average of 112.7 cm, and two dominant groups were found at 80.0 ~ 90.0 cm and 100.0 ~ 140.0 cm (75%); The raw weight (RW) varied between 2.0 and 72.0 kg with dominant groups at 5~10kg and 15~40 kg (68.6%), and the average weight was 26.5 kg. However, body size differed greatly between female and male T. albacares . (2) The relationships between RW and FL and dressed weight (DW) were RW=1.159×10-5FL3.070 and RW=1.118DW+0.684 respectively. (3) The sex ratio of female to male was 1∶1.2, but there were significant differences between size-different groups (χ2=1 093.386，P<0.001). The male was dominant in number when FL was over 140 cm. (4) Gonad samples were mainly at stage Ⅱ (about 50%). The length at 50% maturity (FL50%) was estimated to be 113.4 cm and 34.0% of individuals at greater FL had achieved stageⅤ~Ⅵ gonad maturity, indicating that the stock near Solomon Islands was in spawning period during the survey. (5) Based on the stomach content analysis, we found that T. albacares mainly preyed on fish (67.5%), cephalopods (18.0%) and crustaceans (14.5%), and the empty-stomach ratio was about 51.6%. Significant differences in feeding levels were found between FL groups (χ2=400.782，P<0.001).