The invention provides a novel phosphorus-free corrosion inhibitor which is an organic compound with a novel structure. The structure ensures the phosphorus-free, non-toxic and non-pollution of the agent. The agent molecules and the metal surface form multi point absorption or chelate through nitrogen points in the molecules and other hydrophilic group. The thickness of the film-forming is ensured through the long-chain alkane in the molecules. The short-chain alkane form a cross connection in the film-forming process to enhance the compact degree of the film. On the premise that the corrosion inhibitor is ensured to be free from phosphorus by using the method, the corrosion inhibition property of the corrosion inhibitor can be improved.