The invention relates to a preparation method of a catalyst for preparing high-purity hydrogen by biomass low-temperature gasification. The method is characterized in that weighed soluble calcium saltand nickel salt are dissolved in deionized water, and are fully and uniformly stirred, a mixed solution is placed in a refrigerator for pre-refrigeration until the solution is completely refrigerated, a refrigerated sample is placed in a vacuum freezer dryer for low-temperature vacuum drying to from uniform solid powder, calcining is carried out in a muffle furnace, the calcined product is groundto powder, the powder is placed in a tubular furnace, a reduction reaction is reduced and is characterized in that under certain temperature, hydrogen with a certain volume fraction is introduced until nickel oxide is completely reduced to a nickel simple substance; and a hydration reaction is carried out and is characterized in that water vapor is introduced until calcium oxide is completely conversed to calcium hydrate. The catalyst is suitable for pyrolysis gasification for hydrogen-production under conditions of low temperature and normal pressure, and after biomass pyrolysis gasification, the biomass is mainly conversed to H2 and CO with small molecules and a few of carbon deposit. Compared with the catalyst through traditional biomass gasification, usage temperature is low, catalytic activity is high, cost is low, and industrial usage is easily realized.