The invention discloses genetically engineered bacteria realizing high-density fermentation co-production of 2,3-butanediol as well as a construction method and an application thereof. The genetically engineered bacteria are constructed by integrating three key enzyme genes such as alpha-acetolactate synthetase encoding genes, alpha-acetolacetate decearboxylase encoding genes and 2,3-butanediol dehydrogenase encoding genes onto Escherichia coli chromosomes in a 2,3-butanediol synthesis path. According to the strain fermentation process, the content of the byproduct acetic acid is reduced, so that high-density fermentation can be realized, and 2,3-butanediol with high additional value is co-produced. In addition, the invention also discloses a method for realizing high-density fermentation co-production of other compounds and 2,3-butanediol genetically engineered bacteria and an application thereof. The 2,3-butanediol can be produced by virtue of high-density fermentation, and polyhydroxyalkanoates or functional proteins also can be co-produced, so that low-cost and high-efficiency co-production of the polyhydroxyalkanoates or functional proteins and the 2,3-butanediol is realized, and the genetically engineered bacteria have important industrial application values.