Based on the samples taken from the Chinese squid jigging fishery in the high sea waters of Southwest Atlantic from February to May in 2007, March to May in 2008 and January to March in 2010, annual variability in biological characteristics of squid Illex argentinus were evaluated. For the sampling time periods, this study showed that the sex ratio (female versus males) of catch was between 1. 14-1. 50∶1, and that the mantle length (body weight) of female squid ranged from 188 to 364 mm (110-856g), 200-364mm (145-950g), and 124-276mm (72-425g) respectively, and that the mantle length (body weight) of male squid ranged from 178-298mm (102-703g), 193-314mm (145-680g) and 104-335mm (70-374g), respectively. The sizes of catch in 2010 were much smaller than those in 2007 and 2008. The relationship between mantle length and body weight differed significantly between the sexes and among sampling time years (P<0.001). Significant differences were also found in the composition of sexual maturity in the three years. Meanwhile the significant difference also existed in sizes of catch taken in March over the three years. The average growth rates of mantle length for females and males were 0. 53-1. 07 mm/d and 0. 47-0. 68 mm/d respectively, and the average instantaneous relative growth rates for females and males were 0. 24-0. 41%d^-1 and 0. 23-0. 33%d^-1 . The average growth rate of body weight for females and males were 1. 70-5. 25 g/d and 1. 64-4. 59 g/d, respectively, and the average instantaneous relative growth rates for females and males were 0. 92-1. 37%d^-1 and 0. 86-1. 40%d^-1. The growth indices varied significantly among the years. The relationship between mantle length or body weight and time could be quantified by an exponential growth curve during the fishing seasons. In conclusion, the individuals of the catch in 2007 were from the South Patagonic Stock (SPS); the individuals of the catch in 2008 mainly consisted of SPS squid, but mixed with a small number of small individuals of the Summer-Spawning Stock (SSS); while the SSS made the major contributions to the catch in 2010 with the presence of a small number of SPS. This study suggests a large annual variability in key biological parameters of squid targeted by the Chinese squid jigging fishery in the Southwest Atlantic Ocean.