CDs@ZIF-8 nanocomposites are designed and synthesized as nanoenzymes by a novel one-pot synthetic method in solvent-free system, in which ZIF-8 framework protects CDs from the aggregation and quenching, increasing the participation of CDs for catalytic reactions. The embedding of CDs into ZIF-8 matrix is conducted to rapid electron transfer, and their synergetic effect promotes the composite materials to have superior peroxidase-like activity. CDs@ZIF-8 materials have catalyzed the oxidation of a typical colorimetric substrate 3,3′,5,5′-tetramethylbenzydine (TMB) in the presence of H₂O₂ with the color changes from colorless to blue oxidized TMB (ox-TMB). A colorimetric approach could be established to detect H₂O₂ and glutathione (GSH) due to the outstanding peroxidase-like activity of CDs@ZIF-8-a. This work gives a feasible strategy for the synthesis of CDs-based composite nanozyme with enhanced catalytic activity and thus broadens the application of CDs@MOFs materials in biological analytical field.