The invention discloses an engineering bacteria of inactivated acetolactate synthetase, and a construction method and applications thereof in producing 1,3-propanediol. The acetolactate synthetase in wild type strain for producing 1,3-propanediol is silenced by utilizing homologous recombination and gene insertion inactivation methods, thus obtaining 2,3-butanediol metabolic pathyway-blocked engineering bacteria. By using the engineering bacteria to ferment and produce 1,3-propanediol, the production of side product 2,3-butanediol can be greatly reduced, the metabolism shunting effect of the side product 2,3-butanediol can be greatly decreased, and the conversion rate for producing 1,3-propanediol can be improved; in addition, the side product 2,3-butanediol is reduced to lower the post-extraction pressure, so that the production cost can be lowered. Proved by experiments, the concentration of 1,3-propanediol can achieve 72g / L by fermenting the engineering bacteria for 36 hours through adopting a conventional method. The engineering bacteria and the construction method and applications thereof can play an important role in the industrial production of 1,3-propanediol through adopting a microbial fermentation method, and have wide application prospects.