Two-dimensional (2D) molybdenum disulfide (MoS 2 ) nanomaterials have emerged as promising candidates for constructing excellent supercapacitors, but the lack of large-scale, efficient and low-cost methods for preparing MoS 2 nanosheets severely hinders its practical application. This study demonstrates an accessible and efficient approach for electrochemical exfoliating bulk MoS 2 into high-quality MoS 2 nanosheets with size distribution in the range of 1–3 μm and a thickness of several nanometers in an easily available inorganic salt solution. Furthermore, we construct symmetric all-solid-state supercapacitors based on exfoliated MoS 2 nanosheets. The 2D structure will provide stable channels to facilitate the intercalation/desorption of ions during charge and discharge, and to a certain extent can prevent deposition and agglomeration. Therefore, compared with the unexfoliated MoS 2 , as-prepared MoS 2 nanosheets show great improvement in supercapacitor performance (the specific capacitance increases from the original 130 F g −1 to 215 F g −1 at 5 A g −1 , for instance). In detail, the electrode possesses a specific capacitance of 285 F g −1 at a current density of 2 A g −1 and maintains the great capacitance retention of 83.8% at 8 A g −1 . Moreover, the supercapacitor exhibits a high energy density of 136.8 Wh kg −1 at a power density of 2550 Wh kg −1 . This work provides basic research on the preparation of 2D nanomaterials by electrochemical exfoliation.