To increase the specific capacitance of supercapacitors, polyaniline (PANI) has been chosen as additive electrode material for the pseudocapacitive performance. Here, we synthesize a molecular-level uniform reduced graphene oxide/PANI (rGO/PANI) composite film with high flexibility and conductivity via self-assembly and specific thermal reduction, which performs great potential in flexible supercapacitors with high areal capacitance. Particularly, the electrode of rGO/PANI-42.9% exhibits a high specific areal capacitance (1826 mF/cm2 at 0.2 mA/cm2), and it also presents a good cycling stability (it remains 76% of its initial capacitance after 10500 cycle). Moreover, the specific gravimetric capacitance of rGO/PANI-33.3% reaches up to 256.4 F/g at 0.2 A/g, showing greatly enhanced performance compared with the pure rGO electrode (183 F/g). The results of various characteristic analysis demonstrate that electrochemical performance of the as-prepared rGO/PANI film is closely associated with the uniform distribution of PANI in rGO/PANI composite. Overall, our reported method is convenient and environmental-friendly, and could be beneficial for the development of high-performance capacitive energy storage materials.