The invention provides a phosphoramido pyridine derivative represented by a structural formula (I) and salt thereof. In the formula, R1 represents a hydrogen atom, a halogen atom, cyano, amino, R4-NH-, R5-O-, C1-6 alkyl, hydroxyl C1-6 alkyl, C1-6 alkoxy or C1-6 alkoxy C1-6 alkyl; R4 represents C1-6 alkyl, hydroxyl C1-6 alkyl or C1-6 alkoxy C1-6 alkyl; R5 represents C1-6 alkyl or C1-6 alkoxy C1-6 alkyl; R2 and R3 are selected from a hydrogen atom, C1-6 alkyl or C1-6 alkoxy, or R2 and R3 form a C3-8 ring; and X represents a single bond, methylene, an oxygen atom, a sulphur atom, -CH2O-, -OCH2-, -NH-, -CH2NH-, -NHCH2-, -CH2S- or -SCH2-. The invention also provides a preparation method of the phosphoramido pyridine derivative and the salt thereof, a medical composition using the phosphoramido pyridine derivative and the salt thereof as the active ingredient, and application thereof in the preparation of antifungal medicaments. Compared with the conventional clinically applied antifungal medicaments, the compound has the advantages of high efficiency, low toxicity, wide antifungal spectrum, high physical and chemical property, fine in-vivo antifungal activity and the like.