A linker-drug represented by formula (I). In formula (I), C is a conjugating linker, L is a linker unit, D is a drug unit, and n is an integer ranging from 1 to 4. The structure of the conjugating linker is represented by formula (II). In formula (II), X is a leaving group, both of R1 and R2 are single bond or -NH- and Z is aryl, substituted aryl, heteroaryl, substituted heteroaryl, linear alkyl, cycloalkyl, heterocycloalkyl, or a combination thereof. The wave line of formula (II) indicates the covalent attachment site to L. The antibody is conjugated to the linker unit through a cysteine residue of the antibody. An antibody-drug conjugate (ADC) is also provided. C-(L-D)m (I)
