Based on the 539 samples of Sthenoteuthis oualaniensis collected by Chinese squid jig fishing fleets during April to June of 2013 in the high seas nearby the equator, the biological characteristics were studied. The result indicated that the mantle length (ML) ranged from 137 mm to 338 mm with a high concentration in 160 mm to 220 mm accounting for about 81.45% of all the samples, and the body weight (BW) ranged from 95 g to 1 300 g with a dominative weight from 150 g to 452 g accounting for about 80.76%, respectively. The composition of ML and BW was different among different months, and the dominative ML and BW range increased with the month increase. The ratio of the somatic body weight (SBW) to BW ranged from 40.57% to 87.76% with an average of 59.43%. The relationship between the ML to BW and ML to SBW was best described by the power function and exponential function by the Akaike's information criterion (AIC), respectively. The ratio of females to males was 76:1, and the samples were mostly composed of maturity individuals accounting for about 68.83% of all the samples.However, the maturity stage differed from month and increased with the month increase. The feeding stage was mainly in 0, 1 and 2 grades accounting for 89.42% of all the samples and the food was mainly composed of squids, crustacean and immature fishes.