The invention belongs to the technical field of oilfield reservoir reformation, and particularly relates to an expansive temporary plugging agent and a preparation method thereof. The expansive temporary plugging agent is prepared from raw materials comprising following substances: 20wt%-30wt% of acrylamide, 15wt%-20wt% of 2-acrylamide-2-methyl propanesulfonic acid, 1wt%-5wt% of acrylic acid, 1wt%-2wt% of starch, 4wt%-6wt% of sodium hydroxide, 0.01wt%-0.05wt% of N, N-methylene bisacrylamide, 0.01wt%-0.05wt% of an organic zirconium cross-linking agent and the balance of water. The expansive temporary plugging agent can plug cracks very well in a using process, and has higher expansion character, pressure-bearing property, temperature resistance and acid resistance.