The invention discloses an anti-crack corrosion-resistant concrete admixture as well as preparation and an application of the anti-crack corrosion-resistant concrete admixture. The anti-crack corrosion-resistant concrete admixture is prepared from the following raw materials by weight: 1.5-2.5 parts of fiber comprising a polypropylene fiber, a polyethylene fiber and a carbon fiber, 90-95 parts of an active mineral additive comprising a coal ash, metakaolin, slag and silica fume, and 3.5-7.5 parts of a reactive activator comprising nano dysprosium oxide, nano lanthanum oxide and nano yttrium oxide, the anti-crack corrosion-resistant concrete admixture is doped in a concrete, the weight ratio of a cement in the concrete is 10-40%, a proper amount of a polycarboxylic acid water reducer is added, and the specific doping amount is determined according to the coastal engineering. The pore structure of the concrete is thinned, the corrosion of harmful ions is reduced, the long-term strength of the concrete is guaranteed to improve stably, the carbon dioxide is absorbed, the peaceability, the compactness, the corrosion resistance, the early strength and the anti-cracking ability of the concrete are improved, the service life of the coastal engineering is prolonged, and the economic, social and ecological effects are better.