MgO modified CuZnAl catalysts were prepared by coprecipitation method. The structure and physic-chemistry properties were characterized by BET, XRD, SEM, H2-TPR and CO2-TPD. The catalytic performance of MgO modified CuZnAl catalysts for methanol decomposition to hydrogen was evaluated in a fixed-bed reactor. The results showed that the addition of MgO to CuZnAl catalysts increased BET surface area of the catalysts and CuO dispersity， modified the redox property of catalysts and enhanced the catalytic activity and selectivity. The optimization catalyst was achieved as CuZnAlMg2, with mass ration of m(CuO):m(ZnO):m(Al2O3):m(MgO) = 16:13:3:2. The conversion of methanol decomposition was 99.1% and the gas recovery were 97.0% over CuZnAlMg2 under the reaction condition of reaction temperature 280℃, reaction pressure 1.0 MPa and LHSV 0.6h-1. The analysis to liquid products of methanol decomposition showed the adding suitable amount of MgO improved the alkalinity of catalysts, effectively inhibited liquid by-products and increased the gas yield.