Nanostructured plate-like island molybdenum sulfides (MoSx) film has been synthesized successfully through a facile one-step electrodeposition method from the mixture solution of N, N-dimethyl-formamide (DMF) and H2O. The effect of different ratio of DMF to H2O on the MoSx film has been investigated. Scanning electron microscopy (SEM) shows that when the ratio of DMF to H2O is 1:20, the as-prepared MoSx film exhibits maximum island structures, exposing most edges and rims. The electrochemical measurements confirm that MoSx film deposited in the mixed solution of V-DMF: V-H2O = 1:20 has the best hydrogen evolution reaction (HER) activity, with an overpotential of 80 mV. The improved HER activity may be attributed to the polarity difference of DMF-H2O and morphology directing of DMF. Therefore, using DMF-H2O mixture solution with the appropriate ratio may be a facile and effective way to prepare the excellent electrocatalysts for HER. Copyright (c) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.