The invention provides a reduction-responsive amphiphilic block polymer and its nano-micelle and use. The chain of the reduction-responsive amphiphilic block polymer comprises a hydrophilic polymer and a hydrophobic polymer. The hydrophilic polymer and the hydrophobic polymer are linked by a sulfur-sulfur bond with reducibility. The amphiphilic block polymer can be processed to form reduction-sensitive nano-micelle and the nano-micelle is used for pharmaceutical carriers. A reduction-sensitive sulfur-sulfur bond is arranged at the middle of the amphiphilic block polymer and thus the amphiphilic block polymers self-assemble to form the reduction-sensitive nano-micelle. The reduction-sensitive nano-micelle has a small critical micelle concentration and is not easy to dissociate outside cells and in blood so that the nano-micelle-encapsulated drug is stable. The reduction-responsive amphiphilic block polymer solves the problem that the drug in the human body is easy to leak, carrying efficiency is low and cycle time is short.