A LaNi4.25Al0.75/SiO2 composite was prepared by fumed silica encapsulation method. Microstructure and hydrogen absorption kinetics during hydriding-dehydriding cycling in H2 with 50 mg/L CO were investigated. The results show that apart from large amount of absorbed CO, the surface of LaNi4.25Al0.75 was covered by NiO, La(OH)3, La2O3 and Al(OH)3. Although the capacity and kinetics of both the LaNi4.25Al0.75 and LaNi4.25Al0.75/SiO2 composite were deteriorated after absorption/desorption cycling in the mixed gas, the latter has better poisoning resistance performance