Guanine-rich DNA strands have the potential to activate Cu2+ ions in peroxidase-like reactions based on the coordination of Cu2+ with nucleobases. Comparative studies on the number of guanines elucidate a sequence dependency that contiguous guanines are crucial to intrinsic peroxidase mimicking activities of DNA-Cu(II). The optimal number of repeat units to boost the enzyme-like activity of Cu2+ is identified via analyzing individual sequence of (T(3)G(2))(n) and (T(2)G(3))(n). The catalytic performance of DNA-Cu(II) was found to be remarkably pH-tolerant through the H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine at acidic pH, dopamine at neutral pH as well as methylene blue at alkaline pH, respectively. It is the first time to report that intrinsic peroxidase-like activities of DNA-Cu(II) are greatly associated with binding affinity and stoichiometry between Cu2+ and DNA. (T(3)G(2))(4)-Cu(II) with a dominant 1:1 stoichiometry shows the K (m) toward H2O2 of 93 mM at pH 4.0 and 8.65 mM at pH 11.0. This study paves a way to rationally design artificial metalloenzymes, and the ability to tune the enzymatic activity would be harnessed for biocatalysis, biosensing, green synthesis and nanoscience. Remarkable pH-tolerant peroxidase mimetics was constructed by direct coordination of Cu2+ within a guanine-rich DNA scaffold, of which the enzymatic activity is greatly associated with binding affinity and stoichiometry between Cu2+ and DNA. Intriguingly, there exist optimal guanine numbers and strand lengths to boost the catalytic performance of Cu2+. [GRAPHICS] .