Developing scalable and robust electrocatalysts for hydrogen evolution reaction (HER) for replacement of the Pt-based materials is one of the key issues in producing affordable hydrogen (H2) fuel. Here, we report that titanium dioxide (TiO2), a typical low-cost and earth-abundant transition metal oxide, is triggered to be an active material for catalyzing HER. A modified TiO2 with high amount of defects in its surface (TiO2-m) is prepared via H2 plasma treatment of pristine mesoprous TiO2 (TiO2-p), which exhibits competitive HER activity in alkaline media. Further experimental analysis and theoretical calculation reveal that high concerntration of surface defects (Ti3+ species) is the critical factor for activating the catalytic performance of TiO2-m, which simultaneously result in its dramatically enhanced electric conductivity, larger electrochemical active surface area (ECSA), and the modest hydrogen-intermediate adsorption energy. It is believed that this study might provide a versatile pathway to design surface defected metal oxides as more practical non-Pt catalysts.