Pseudocapacitive electrode materials employed in supercapacitors may bring in high energy density (ED) and specific capacitance (Csc), which are critical for their practical applications. Accordingly, logical design of advanced electrode materials is highly demanded to progress high-performance supercapacitors. Here, for the first time, we suggest a straightforward route for the synthesis of NiGa2S4-rGO as an advanced cathode material supported on nickel foam (NF) for employed in flexible solid-state asymmetric supercapacitors (FSASCs). Due to an abundant ratio of active sites and large surface area of the NiGa2S4-rGO advanced material, the as-prepared NiGa2S4-rGO/NF electrode illustrates considerable electrochemical properties including remarkable specific capacitance (Csc) of 2124.34 F g−1 with excellent rate capability of 73%, and exceptional durability, which are better than NiGa2S4/NF and previously reported transition metal sulfides (TMSs). Furthermore, for the first time a pseudocapacitive advanced anode material of FeSe2-rGO have been successfully fabricated on a nickel foam (NF) substrate by a facile strategy. Element Selenium as the favorable element was offered into the Fe for enhancement and adjustment of the anode material electrochemical performance. The FeSe2-rGO/NF advanced anode electrode presents satisfactory electrochemical properties containing an exceptional specific capacitance (Csc) of 432.40 F g−1, significant rate performance of 57.84% and superior durability, which are better than FeSe2/NF electrode and previously studied Fe-based anode material. Considering the remarkable electrochemical performance of the as-prepared pseudocapacitive advanced electrode materials, a FSASC based on the NiGa2S4-rGO/NF as the cathode electrode and FeSe2-rGO/NF as the anode electrode was assembled. The FSASC device delivers superior Csc of 341.20 F g−1, outstanding energy density (ED) of 121.31 W h kg−1, remarkable cycle stability (only 7.30% damage after 5000 charge/discharge (CD) cycles).