The invention provides a preparation method of an alkalosis-preventing copper-based spinel low-temperature denitration catalyst. The preparation method comprises the following steps: firstly, inhibiting hydrolysis of a precursor through a mixed acid method and uniformly dispersing the precursor in a solution; then forming copper-based spinel through enriched oxygen atmosphere calcining; and finally, regulating the activity on the copper-based spinel through reduced atmosphere calcining to obtain the copper-based spinel low-temperature denitration catalyst with efficient SCR catalytic activityand alkalosis-preventing ability. Cu and one or more of Al, Ga, Mn, Fe, Cr and Co form a spinal phase which becomes the active ingredient of the catalyst. The method has the advantages that 1, hydrolysis of the precursor can be inhibited by means of the mixed acid method and the dispersibility of the active ingredient is improved; 2, the active ingredient is regulated by two ways, the defects of the spinel structure are designed by adopting a reducing atmosphere and replacement is carried out by isomorphism by means of different metal ions; and 3, the alkalosis-preventing ability of the copper-based spinel catalyst is enhanced by means of the structural characteristic of the spinel.