The invention relates to a high temperature swellable granule plugging agent and a preparation method thereof. The raw materials include, by mass, 20-50% of acrylamide, 20-50% of acrylic acid, 1-15% of sodium hydroxide, 2-10% of inner rigid particles, 0.1-0.5% of ammonium persulfate, 0.05%-0.25% of sodium bisulfite, 0.1-0.5% of N, N-methylene-bisacrylamide, 1-5% of dodeyl methacrylate and the balance water. The high temperature swellable granule plugging agent provided by the invention has the plugging mechanism of ordinary profile control agents used as profile control and water plugging agents, has a flexible outer layer, and can deform and advance in stratum, when the flexible outer layer is destroyed and lose efficacy, the internal rigid inner core still can form effective plugging to the stratum so as to realize stratum successive deep profile control and flooding, thus reaching the purposes of twice plugging and increase of plugging time. The high temperature swellable granule plugging agent is applicable to a stratum temperature below 200DEG C, has a water-absorbent expanding multiple of 20-40 times and a rock core plugging rate of greater than 98%, and after 10PV (pore volume) injected water scouring, the plugging rate still remains above 96%. The high temperature swellable granule plugging agent is suitable for profile control and water plugging of ordinary oil-water wells, and also can be applied to profile control and channel plugging of heavy oil thermal recovery wells.