Illex argentinus is an important target species for Chinese squid jigging fleets in the southwest Atlantic,and the accurate forecasting of fishing ground can provide better scientific guidance for fishing activities. In this study, according to the Chinese squid fishing production data during the main fishing season (January to May) from 2000 to 2005, combined with sea surface temperature (SST) and chl.a accordingly, the percentage of fishing times and daily catch (CPUE) will be considered as the suitability index (SI). Using arithmetic mean model (AM) to establish the integrated habitat suitability index (HSI) based on SST and chl.a from 2000 to 2004, and the fishing and environmental data were used to test the established HSI model from January to May in 2005. The results indicated that AM model is fitted well. According to the data from January to May in 2005, we found that the main fishing ground is distributed in the waters with HSI more than 0.6 from the AM HSI model, and its percentage of fishing times reached more than 76 percent and its average CPUE were above 7.6 t/d. The results showed that the AM HSI model based on SST and chl.a can better predict the fishing grounds of squid in the southwest Atlantic and the accuracy rate of forecasting fishing ground reaches more than 70%.