The invention discloses a bacterial strain capable of rapidly degrading nitrogen in sewage, and applications of the bacterial strain, belonging to the technical field of environment engineering. According to the invention, paracoccus denitrificans DYTN-1 capable of rapidly degrading nitrogen in sewage can be obtained through screening, the inorganic nitrogen component harmful to cultured organisms in a water environment can be controlled by the bacterial strain, and the ecological environment of a cultured water body can be rapidly restored, thus creating a good water body environment for aquacultured organisms. The paracoccus denitrificans DYTN-1 can be directly applied to nitrogen removal by denitrification for nitrate-containing nitrogen waste water, and can also be applied to nitrogen removal of ammonia-nitrogen-containing waste water, thus being a bacterium with a heterotrophic nitrification-aerobic denitrification function. After the bacterium is invested and used, the starting time of the system can be shortened, and the paracoccus denitrificans DYTN-1 has wide application prospects in various waste water nitrogen removal treatment processes, and is especially suitable for biological nitrogen removal technology of synchronized nitrification and denitrification.