The invention relates to a method for preparing acrylic acid-acrylamide copolymer initiated by plasma. Air is ionized to be plasma under normal pressure, meanwhile, the plasma is put into a reaction vessel containing aqueous solution of acrylic monomer and acrylamide, the flow rate of air is 10-50ml/min. Discharging is carried out for polymerizing for 10-20 min; absolute methanol precipitant is added to terminate reaction after polymerizing for 1-2 hours, repeated washing is carried out with the absolute methanol to remove the unreacted monomer, and vacuum drying is carried out for 24-48 hours. The invention uses plasma to initiate polymerization without an initiator, the product is very pure and has wide development prospect and realistic significance.