Herein, the ternary composites, ultrasmall metal nanoparticles encapsulated in the anionic metal-organic frameworks/electrochemically reduced graphene oxide (MNPs@Y-1, 4-NDC-MOF/ERGO, M = Ag, Cu) are constructed by a cationic exchange strategy and an electrochemical reduction process for the electrochemical determination of HO. Both AgNPs@Y-1, 4-NDC-MOF/ERGO and CuNPs@Y-1, 4-NDC-MOF/ERGO display excellent electrocatalytic activity toward HO, but the former is superior to the latter. Such a difference in electrocatalytic activity can be explained by the characterization measurements, and the results manifest MNPs@Y-1, 4-NDC-MOF/ERGO (M = Ag, Cu) electrocatalysts have subequal MNPs sizes and electrochemical surface areas, but different electron transfer rate constants. The AgNPs@Y-1, 4-NDC-MOF/ERGO sensor shows a linear detection range from 4 to 11,000 μM with the detection limit of 0.18 μM. Moreover, MNPs@Y-1, 4-NDC-MOF/ERGO (M = Ag, Cu) exhibit excellent anti-interference performance and can be used for the detection of HO released from living cells. The proposed sensor takes full advantage of the catalytic property of MNPs, the size selectivity of Y-1, 4-NDC-MOF, and the fast electron transport effect of ERGO. Thus, the MNPs@Y-1, 4-NDC-MOF/ERGO/GCE (M = Ag, Cu) can be utilized to detect oxidase activities by monitoring HO produced in the presence of substrate and oxidase, and it is expected that composites with the molecular sieving effect and catalytic activity can be widely applied for catalysis, biomedicine, and biosensing fields.