AbstractPolysulfides are significant compounds in life science, pharmaceutical science, and materials science. Therefore, polysulfide construction is in great demand. The controllable sequential installation of groups on both ends of a S−S motif faces an enormous challenge owing to the reversible nature of the covalent S−S bond. A library was established with two divergent mask groups for bilateral unsymmetrical disulfurating reagents (R1O−SS−SO2R2). Sequential coupling with preferential activation of the S−SO2 bond (37.6 kcal/mol) and controllable activation of the S−O bond (54.8 kcal/mol) in the presence of the S−S bond (62.0 kcal/mol) enabled successive reactions at each end of the S−S motif to afford unsymmetrical disulfides and trisulfides, even for the cross‐linkage of natural products, pharmaceuticals, peptides, and a protein (bovine serum albumin).