Abstract: In base of 901 individuals of Argentine shortfin squid (Illex argentinus) collected in continental shelf and slope of southwest Atlantic by twin trawls during January to April in 2011, we determined their population composition, feeding intensity, length-weight relationship and gonadal development. The results show that the mantle length of the samples increases along with the sampling time. Feeding ability of small-mantle-length groups is weaker than that of big-mantle-length ones, which is related with fecundity peak period. The mantle length of first maturity for females and males is 191.6 mm and 182.6 mm, respectively. The average mantle length in maturity Stage Ⅴ is shorter than that in Stage Ⅲ and Ⅳ. The results suggests that the catch is composed of south Patagonia stock (SPS) and summer spawning stock (SSS), and recruitment of some big-mantle-length summer population is found in post trawling.