The invention discloses a composite catalyst for preparing hydrogen-rich gas through biomass gasification and a preparation method thereof. The composite catalyst comprises the following components in parts by weight: 5-20 parts of NiO, 5-10 parts of CeO2, 5-10 parts of ZrO2, and 60-80 parts of dolomite. The preparation process comprises the steps of carrier pretreatment, introduction of a main active component, introduction of an auxiliary active component and forming of the catalyst. The composite catalyst prepared by the method disclosed by the invention has a high H2 volume fraction during gas generation, and has high catalytic activity, good strength, strong anti-sintering and anti-carbon deposition capabilities, and the like.