Abstract: The present invention relates to a conjugate of a cytotoxic drug/molecule to a cell-binding molecule with a bis-linker (a dual-linker) containing a 2,3-diaminosuccinyl group. It also relates to preparation of the conjugate of a cytotoxic drug/molecule to a cell-binding molecule with the bis-linker, particularly when the drug having functional groups of amino, hydroxyl, diamino, amino-hydroxyl, dihydroxyl, carboxyl, hydrazine, aldehyde and thiol for conjugation with the bis-linker in a specific manner, as well as the therapeutic use of the conjugates.