In this work, graphene film is readily produced by an in-situ chemical reduction method, which involves simultaneous film formation and chemical reduction. In terms of versatility, graphene films produced with different types and doses of reductants, different thicknesses and areas are also successfully produced by this in-situ chemical reduction method. The graphene film produced with reductant of HI/CH3COOH (G(HI/CH3COOH)) has the highest electrical conductivity of 6900 S m-1 and unique loose multilayered structure, and also exhibits excellent capacitive performance. Typically, the supercapacitor based on G(HI/CH3COOH) exhibits the highest areal capacitance (CA) of 152.4 mF cm-2 at 2 mA cm-2 and good rate performance (89% retention at 8 mA cm-2). Notably, the CA has no decay with the areas of G(HI/CH3COOH) increased from 1×1 cm2 to 5×5 cm2, indicating the highly electrical conductivity and uniformity of produced G(HI/CH3COOH). In addition, the flexible solid-state supercapacitor with fascinating cycling stability (97% retention after 10000 cycles) and electrochemical stability (negligible capacity loss after 4000 bending cycles) is also obtained by employing the G(HI/CH3COOH) electrode material and polymer electrolyte. These results demonstrate that the in-situ chemical reduction method produced graphene film holds great potential for applications in wearable energy storage devices.