The invention discloses a preparation method of a Mn-Ti oxide system low-temperature selective catalytic reduction (SCR) catalyst. The preparation method comprises the following steps of: in a stirring condition, adding titanium tetrabutoxide in acrylic acid to uniformly mix, adding manganous nitrate and a solvent, and stirring a mixture to form a homogeneous phase solution, wherein a mol ratio of the titanium tetrabutoxide to the manganous nitrate ranges from 10: 1 to 10: 6, and a mol ratio of sum of the titanium tetrabutoxide and the manganous nitrate to the acrylic acid ranges from 1: 5 to 1: 1; deoxidizing by introducing nitrogen, and adding an initiator to polymerize, so as to obtain solid polyacrylate; and drying and carrying out pyrolysis on the solid polyacrylate, and then grinding to obtain Mn-Ti oxide powder. The preparation method provided by the invention has the advantages of easiness of control and convenience in implementation; metal ions in a prepared polymer precursor can be horizontally and uniformly mixed in an ion level; the grain size of the Mn-Ti oxide powder prepared by sintering the polymer precursor can reach a nanometer level and a narrow distribution range so that the Mn-Ti oxide system low-temperature SCR catalyst has a better application prospect in a low-temperature smoke SCR denitration reaction catalyst field.