The invention discloses a modified maltose syrup retarder as well as a preparation method and application thereof. The modified maltose syrup retarder is prepared from maltose syrup, acrylic acid, an activating agent, unsaturated acid, esters, acrylamide, an initiator, deionized water and liquid caustic soda in a mass part ratio of (79-157):(10-40):(0.5-3.2):(40-80):(20-40):(20-40):(1-5):(500-750):(8-15). The preparation method comprises the following steps: putting malt syrup and acrylic acid into a No.1 reaction kettle according to the mass part ratio of (4-8):1, further adding an activating agent which is 0.5-2% of the total amount of the malt syrup, heating to 70-90 DEG C, stirring and reacting for 4 hours, and cooling to room temperature to obtain an intermediate product A; then adding the intermediate product A, unsaturated acid, esters, acrylamide, an initiator and deionized water in a mass ratio of (100-200):(40-80):(20-40):(20-40):(1-5):(500-750) into a No.2 reaction kettle, heating to 85-90 DEG C, stirring the mixture to react for 4 hours, cooling a reaction product to room temperature, and regulating the pH value to be about 7 by using liquid caustic soda to obtain the modified malt syrup retarder.