Molybdenum disulfide (MoS2) possesses promising prospects of application in electrocatalytic hydrogen evolution. However, the MoS2 prepared by traditional hydrothermal method is usually 2H (hexagonal) semiconducting state with limited active sites and unsatisfied conductivity, hindering the improvement of hydrogen evolution efficiency. Herein, the MoS2 nanoflowers are in-situ grown successfully on graphite felt (GF) by hydrothermal method, and a simple and effective electrochemical activation is proposed to enhance the hydrogen evolution activity of the composite. The electrical activation in acidic medium guides the intercalation of protons between MoS2 and GF, and the increased interlayer spacing between MoS2 is conducive to the adsorption and release of hydrogen. The synergistic effect between MoS2 and GF is enhanced, resulting in accelerated electron transfer through S sites in MoS2 and oxygen-containing functional group in GF. The experimental results and density functional theory (DFT) computations demonstrate that the electrical activated catalyst possesses excellent electrocatalytic activity and long-term operation stability (Tafel slope is 48 mV dec(-1), the overpotential is 82 mV at current density of -10 mA cm (2)). Our research confirms the electrochemical activation is a simple technique for enhancing the hydrogen evolution efficiency of MoS2/GF composite as well as other transition metal chalcogenides and carbon materials. (C) 2019 Published by Elsevier Inc.