Plastic-used high-flowability modified calcium carbonate comprises the following raw materials by weight: 0.3 to 0.4 part of sodium bicarbonate, 0.5 to 0.8 part of stannous chloride, 1 to 1.3 parts of sodium polyacrylate, 2 to 3 parts of nano iron-ore slag, 1 to 2 parts of isopropyl palmitate, 0.5 to 0.8 part of pre-gelatinized starch, 0.7 to 1 part of magnesium stearate, 0.5 to 0.8 part of cerium dioxide, 200 to 220 parts of heavy calcium carbonate, 5 to 9 parts of additives, and 20 to 30 parts of water. The modified calcium carbonate is simple in modification method, and is uniformly modified, and is higher in flowability and compressibility due to the addition of stannous chloride, isopropyl palmitate, pre-gelatinized starch, white dextrin and magnesium stearate, thereby ensuring uniform piece weight during a tabletting step and reducing the size of tablets under the same condition; due to the addition of cerium dioxide, the oxidation resistance and the abrasion resistance of plastic adopting the high-flowability modified calcium carbonate can be enhanced.