Abstract: Using  tetraethylorthosilicate（TEOS），lanthanum  nitrate，and cerium nitrate as raw materials and cetyl-trimethyl- ammonium bromide（CTMAB） as the template agent，MCM-41 mesoporous molecular sieves were synthesized with La or Ce incorporated in the framework under hydrothermal conditions.The structure and the state of Ln-doped MCM-41 were characterized by the analysis of XRD，FT-IR，and nitrogen adsorption-desorption.Its activities of selective catalytic reduction of NO with ammonia as reductant as well as the influences  of lanthanide doping content，temperature，space velocity and n（NH3）/ n（NO） on catalytic performance were investigated.The aim of this work was to incorporate lanthanide to improve de-NOx performance of molecular sieves.Ln-MCM-41 changed skeleton structure，which could increase the number of lattice defects to improve reactivity and pore surface adsorption due to exchangeability of rare earth metal ions.The result  indicated that La and Ce were introduced into the framework of MCM-41 mesoporous materials and maintained an orderly hexagonal pore structure.The order degree declined with the increase of La and Ce doping amounts.Ln-MCM-41 could maintain high activity at 350 ℃ when n（Ln）/n（Si）=0.04，space velocity  was 4 000 h-1 ，and n（NH3）/n（NO）=1∶1.The lanthanide-doped MCM-41 molecular sieves will be helpful in promoting catalyst activity effectively.

Key words: mesoporous molecular sieves, Ln-MCM-41, selective catalytic reduction