The invention discloses a genetically engineered bacterium for efficiently expressing high-molecular weight nitrile hydratase and an application of the genetically engineered bacterium, and belongs to the technical field of microbiological genetic engineering. The high-molecular weight nitrile hydratase gene nhhB (rbs) A (rbs) G is obtained from a nitrile hydratase gene bag based on an R.rhodochrous J1 source through codon optimization, express element transformation and chemical synthesis. The whole length of the gene is 1645bp; the gene is encoded with 533 amino acids and can be successfully expressed in escherichia coli; the method is efficient and safe; 96.7U/mL soluble nitrile hydratase can be obtained by inducing at 24 DEG C for 16 hours; the specific enzyme activity can be up to 234U/mg after purification; and the method is beneficial to extraction and purification of the nitrile hydratase and efficient enzymatic synthesis of amide substances in the production process.