In absence of catalysts, Oscillations in the oxidation of KSCN、Na2S2O3 and SC(NH2)2 by H2O2 are observed in CSTR experiments, single-peak and other phenomena are observed in batch experiments. Oscillations in pH and Pt potential are antiphase in H2O2-Na2S2O3-H+ system and H2O2-KSCN-OH- system, but oscillations in pH and Pt potential are synchronous I n H2O2-SC(NH2)2-H+ system.