In order to synthesize a high-efficiency catalytic electrode for hydrogen evolution reactions, nano-MoS2was deposited in situ on the surface of graphite substrates via a one-step hydrothermal method. The effects of the reactant concentration on the microstructure and the electrocatalytic characteristics of the nano-MoS2catalyst layers were investigated in detail. The study results showed that nano-MoS2sheets with a thickness of about 10 nm were successfully deposited on the surface of the graphite substrates. The reactant concentration had an important effect on uniform distribution of the catalyst layers. A higher or lower reactant concentration was disadvantageous for the electrochemical performance of the nano-MoS2catalyst layers. The prepared electrode had the best electrocatalytic activity when the thiourea concentration was 0.10 mol·L−1. The minimum hydrogen evolution reaction overpotential was 196 mV (j= 10 mV·cm−2) and the corresponding Tafel slope was calculated to be 54.1 mV·dec−1. Moreover, the prepared electrode had an excellent cycling stability, and the microstructure and the electrocatalytic properties of the electrode had almost no change after 2000 cycles. The results of the present study are helpful for developing low-cost and efficient electrode material for hydrogen evolution reactions.