Lanthanum oxide/dodecyl sulfate mesoporous material (LaOS) was synthesized by hydrothermal method with SDS as template and ethylenediamine as medium. The experimental results indicate that the material had the ordered mesoporous pore structure when n(La)/n(SDS)/n(CO(NH ₂) ₂)/n(H ₂NCH ₂CH ₂NH ₂)/n(H ₂O)=1.0∶1.0∶0.6∶1.0∶200, stirring at 80 ℃ and 4 h using several measurements such as XRD, IR，TG/DTA,N ₂ adsorption-desorption .The results indicate that the material had the medial pore structure with average pore diameter of 2.6 nm and the specific surface area of 182 m ²/g. The LaOS materials were used as catalysts in the ethoxylation reaction. The results show that the material was highly catalytic activity. Experiment indicates that the optimum processing parameters are :120 ℃, 0.5 MPa,mass fraction of 10% catalyst (LaOS) and average reaction rate of epoxy ethane is 3.7 mol/(mol·h). And narrowed chain distributions of octanol polyoxyethlene were formed in the presence of LaOS catalyst.