The invention discloses an N-methyl lomefloxacin acetal 4-aryl thiosemicarbazide derivative as well as a preparation method and application thereof. The derivative adopts a chemical structural general formula shown as a formula I, wherein the structural formula is as shown in the specification. In the formula I, the substituent group Ar refers to a benzene ring or a substituted phenyl ring or a pyridine ring or a furan ring or a thiophene ring. According to the N-methyl lomefloxacin acetal 4-aryl thiosemicarbazide derivative disclosed by the invention, three excellent pharmacophores such as difluoroquinolones framework, Schiff base imine and thiourea are cohered, so that the antitumor activity of a novel compound is increased, the toxic and side effects on normal cells are reduced, and the derivative can serve as an antitumor active material to develop an antitumor drug of a brand new structure.