Based on the survey from September 21, 2012 through November 15, 2012 in the waters near Cook Islands by Chinese tuna longliner, we analyzed the biological characteristics of albacore tuna, such as fork length distribution, fat content distribution, the temporal and spatial distribution of fat content, and the relationship between fat content and fork length. The results showed: (1) The fork length of the albacore tuna was 0.50-1.14 m, the average fork length was 0.95 m, and dominant with 0.90-0.99 m, accounted for 80.36%; (2) The minimum fat content of albacore tuna was 0.3%, the maximum fat content was 4.6%, and the average fat content was 2.0%, and the size composition was very rich; (3) From September 21 to October 13, 2012, the fat content of albacore tuna was low, while after October 13, 2012, the fat content of albacore tuna increased over time; (4) In the northwest area (11°S-13°S,162°W-168°W), the fat content of albacore tuna (2.7%-3.0%) was higher than that of the other areas (1.0%-2.5%); (5) There was no significant relationship between fat content of albacore tuna and its fork length(0.85-1.14 m, P>0.05). This study suggested: (1) After mid-October, the albacore tuna started to store fat to prepare for spawning; (2) The albacore tuna captured in the survey were mature individuals, basically, and they began to spawn and were migrating from the southern waters to northern tropical waters; (3) The spawning might occur in the northwest area (11°S-13°S, 162°W-168°W) of the waters near Cook Islands.