The invention discloses a high-molecular nanoparticle gas pipeline corrosion inhibition type drag reducer and its preparation method, and relates to the technical fields of general methods in the organic chemistry, corrosion protection of metal materials, and pipeline systems. The drag reducer is formed through adopting methyl methacrylate as a raw material, light polystyrene foams as an adjuvant, deionized water as a reaction medium, sodium hyposulfite as an initiator, sodium chloride as an ion intensity adjusting agent and a polyamine as a surface modifier, and reacting under a reflux stirring condition. The drag reducer comprises 11.04-19.85% by mass of the methyl methacrylate, 0.28-0.5% by mass of the light polystyrene foams, 79.4-88.32% by mass of the deionized water, 0.12-0.14% by mass of the sodium hyposulfite and 0.13-0.22% by mass of the sodium chloride. The high-molecular nanoparticle gas pipeline corrosion inhibition type drag reducer has the characteristics of strong tube wall absorption affinity, obvious reduction of the tube wall roughness, and good effect.