The integration of graphene nanosheets on the macroscopic level using a self-assembly method has been recognized as one of the most effective strategies to realize the practical applications of graphene materials. Here, a facile and scalable method is developed to synthesis two types of graphene-based networks, manganese dioxide (MnO2)–graphene foam and carbon nanotube (CNT)–graphene foam, by solution casting and subsequent electrochemical methods. Their practical applications in flexible all-solid-state asymmetric supercapacitors are explored. The proposed method facilitates the structural integration of graphene foam and the electroactive material and offers several advantages including simplicity, efficiency, low-temperature, and low-cost. The as-prepared MnO2–graphene and CNT–graphene electrodes exhibit high specific capacitances and rate capability. By using polymer gel electrolytes, a flexible all-solid-state asymmetric supercapacitor was synthesized with MnO2–graphene foam as the positive electrode and CNT-graphene as the negative electrode. The asymmetric supercapacitors can be cycled reversibly in a high-voltage region of 0 to 1.8 V and exhibit high energy density, remarkable rate capability, reasonable cycling performance, and excellent flexibility.