t-Boc-N-amido-PEG4-Tos is a PEG linker with dual protecting groups, consisting of an amino group protected by tert-butyloxycarbonyl (t-Boc), a tetraethylene glycol (PEG4) spacer arm, and a tosyl group (Tos). Its production is achieved through solid-phase synthesis or stepwise coupling in solution: starting with the Boc-protected amine, the PEG4 chain is linked via an amide bond, and the Tos group is introduced at the terminus as a leaving group. This reagent is widely used in peptide modification, drug conjugation, and polymer material synthesis. The Tos group can participate in nucleophilic substitution reactions, while the Boc group is removed under mild acidic conditions, enabling stepwise activation of functional groups, effectively avoiding side reactions and improving synthetic efficiency.