Poly(ester-b-ether)s, a kind of meaningful block polymeric materials for biomedicines and self-assembly, are typically synthesized via ring-opening polymerization of cyclic esters initiated by pre-prepared polyether macroinitiator. However, multi-step procedure is required in this traditional method. Herein, we detailed a one-step self-switchable copolymerization process of mixed monomers to precisely prepare poly(ester-b-ether) block copolymer materials. The strategy enables ring-opening alternating copolymerization of anhydrides with epoxides and ROP of epoxides sequentially in a closed system. Regioselective and living copolymerization is realized by cooperative organocatalysts to endow the poly(ester-b-ether) with controlled monomer sequence, high isotacticity and predictable molecular weight. A tandem copolymerization is developed by using lactide as an external trigger which could switch the hierarchically selective copolymerization to lactide polymerization. The study provides a new route to the facile synthesis of poly(ester-b-ether) block copolymer materials using a metal-free catalytic system.