The invention relates to corrosion inhibitor of copper in seawater or sodium chloride solution, i.e. a low-toxin and high-efficiency corrosion inhibitor used for inhibiting corrosion of metal copper and products thereof in seawater or a sodium chloride medium, and application thereof. The effective component is myclobutanil [also know as: 1-(4- chlorphenyl)-2-(1H-1,2,4- pyrrodiazole-1- methyl) amyl cyanide]. The product can prevent the full corrosion and the local corrosion of the metal copper when in contact with the seawater or the sodium chloride solution. Currently, the compound has been applied in industrial production in a large scale, is widely applied to agricultural production, but has not been used for metal corrosion inhibitor. The corrosion inhibitor has the advantages of little used amount, small toxin, high efficiency and strong sustainability, can effectively inhibit the corrosive damage of the metal copper, and has broad application prospect.