Molybdenum carbides embedded on carbon nanotubes are prepared via a simple hydrothermal method with subsequent post-treatment at high temperature. In order to optimize the electrocatalytic activity for hydrogen evolution reaction (HER), effects of hydrothermal and post-annealing temperature are systematically investigated. Electrochemical testing results indicated that Mo2C/CNT prepared at a solvothermal temperature of 200 degrees C and 800 degrees C post heat-treatment exhibits the best HER activity with an overpotential of 125 my in acid media and 93 mV in alkaline media at a current density of 10 mA cm(-2). Such enhanced catalytic activity may originate from high electro-conductivity and ECSA value, together with ultra-small particle size, which accelerates the electron transfer rate and provides large surface area and active sites, respectively.