The invention discloses benzoxazinone derivatives, a synthesis method and applications thereof. The derivatives can be used as an antibacterial agent for treating infectious diseases caused by bacteria, especially tuberculosis (TB) caused by mycobacterium. Specifically, the invention relates to compounds represented by the formula (I), pharmaceutically acceptable salts thereof, and a pharmaceutical composition comprising the provided compounds; wherein the R1 to R4 are defined in the description. The invention aim to prepare novel compounds capable of inhibiting the mycobacterium activity, the compounds can be used as a potential novel drug for treating infectious diseases caused by bacteria, moreover, the compounds can be used to treat or prevent tuberculosis (TB) caused by mycobacterium, at the same time the problems related with drug resistance can be solved, and the drug metabolism property can be improved on the basis that the mycobacterium tuberculosis resistant activity is not influenced.