The invention discloses a preparation method for a catalyst used in preparation of low-carbon olefin from synthetic gas. The preparation method comprises the following steps: (1) with alumina as a carrier, impregnating the alumina carrierin a zinc salt solution by using an unsaturated impregnation method and then carrying out drying and roasting; (2) impregnating the roasted carrier in the step (1) with a wetting solution containing an adsorbent by using the unsaturated impregnation method, wherein the adsorbent is organic amine with a carbon number of 2 to 15 and the addition amount of the adsorbent is 1 to 10% of the weight of the roasted carrier in the step (1); and (3) subjecting the adsorbent-containing carrier obtained in the step (2) to impregnation of a mixed solution containing active metal iron and an auxiliary agent manganese after drying, carrying out drying and roasting, then carrying out unsaturated spraying and impregnation of a metallic auxiliary agent potassium and subjecting the carrier to drying and roasting so as to obtain the catalyst used in preparation of low-carbon olefin from synthetic gas. The catalyst has the characteristics of long-cycle operation activity and high stability and is beneficial for industrial application and promotion.