Carbon aerogel (CA), possessing abundant pore structures and excellent electrical conductivity, have been utilized as conductive sulfur hosts for lithium-sulfur (Li-S) batteries. However, a serious shuttle effect resulted from polysulfide ions has not been effectively suppressed yet due to the weak absorption nature of CA, resulting in rapid decay of capacity as the cycle number increases. Herein, ultrafine (similar to 3 nm) gadolinium oxide (Gd2O3) nanoparticles (with upper redox potential of similar to 1.58 V versus Li+/Li) are uniformly in-situ integrated with CA through directly sol-gel polymerization and high-temperature carbonization. The Gd2O3 modified CA composites (named as Gdx-CA, where x means molar ratio of Gd2O3 nanoparticles to carbon) are incorporated with S. Then, the products (S/Gdx-CA) are acted as sulfur host materials for Li-S batteries. The results demonstrate that adding ultrafine Gd2O3 nanoparticles can dramatically improve the electrochemical properties of the composite cathodes. The S/Gd2-CA electrode (loading with 58.9 wt% of S) possesses the best electrochemical properties, including a high initial capacity of 1210 mAh g(-1) and a relatively high capacity of 555 mAh g(-1) after 50 cycles at 0.1 C. It is noteworthy that the performance of long-term cycle (350 cycles) for the S/Gd2-CA (317 mAh g(-1) after 100 cycles and 233 mAh g(-1) after 350 cycles at 1 C) is improved significantly than that of S/CA (150 mAh g(-1) after 150 cycles at 1 C). Overall, the enhancement of electrochemical performances can be due to the strong polar nature of the ultrafine Gd2O3 nanoparticles, which provide strong adsorption sites to immobilize S and polysulfide. Furthermore, the Gd2O3 nanoparticles present a catalytic effect. Our research suggests that adding Gd2O3 nanoparticles into S/CA composite cathode is an effective and novelty method for improving the electrochemical performances of Li-S batteries.