The metastable crystal structure is difficult to synthesize and maintain but normally acts as special active sites with improved functional properties. Herein, a moderate crystallographic transformation strategy is used to effectively synthesize metastable RuO2. By controlling the degree of oxidation, we constructed different heterophase Ru/RuO2 catalysts. The results show that the metastable fcc-Ru/fcc-RuO2 heterointerphase holds an improved crystal structure matching property accompanied by enhanced water dissociation and appropriate adsorption capacity for intermediates, achieving a current density of 10 mA cm-2 at a low potential of 11.2 mV. This study provides an effective extension for the crystal phase design of catalysts.