Electrochemical energy storage system has been a promising focus to tackle with the current energy crisis problem. Polyaniline (PANI) has been an attractive electrode material in energy storage devices, owning unique and excellent developing prospects in the field of supercapacitors. In order to further improve its capacitive performance, composite materials of PANI blended with various carbon-based materials, metal oxides or metal sulfides are typically prepared. In this study, PANI-based ternary composite of PANI, molybdenum disulfide (MoS2) and graphite powder (Gr) was prepared electrochemically to afford the PANI/MoS2/Gr-modified electrode materials. Cyclic voltammetry (CV), galvanostatic charge and discharge (GCD) and electrochemical impedance spectroscopy (EIS) methods were used to characterize and investigate the ternary composite’s supercapacitive performance. A high specific capacitance of 381.9 F/g was achieved under 1 A/g current density. When the applied current densities were increased from 1 to 8 A/g, a high specific capacitance of 322.0 F/g was still maintained, which corresponded to a good capacitance retention rate of 84.3%, showing the ternary composite’s excellent rate performance. The research results illustrated the great potential of the PANI/MoS2/Gr ternary composite as a promising supercapacitor energy storage material.