The practical applications of flexible supercapacitor depend strongly on the successful fabrication of advanced electrode materials with high electrochemical performance. Herein, three-dimensional conductive network-based self-standing MnCO₃@graphene/CNT hybrid film fabricated through a combination of a hydrothermal method and vacuum filtration for flexible solid-state supercapacitors is reported. The MnCO₃@graphene structure is embedded in a CNT network, in which monodispersed MnCO₃ nanorod is well confined in graphene nanosheets. This hierarchical structure provides rapid electron/electrolyte ion transport pathways and exhibits excellent structural stability, resulting in rapid kinetics and a long life cycle. The MnCO₃@graphene/CNT electrode delivers high specific capacity (467.2 F g^–1 at 1 A g^–1). Asymmetric supercapacitor (ASC) devices are assembled with the MnCO₃@graphene/CNT film as positive electrode and activated carbon/carbon cloth as negative electrode, which exhibits a high energy density of 27 W h kg^–1. Remarkably, 93% capacitance retention is obtained for the ASC devices after 6000 cycles.