The rapid development of various portable and wearable electronics proposes a great demand on flexible supercapacitors. It is critical to develop highly flexible electrode materials for flexible supercapacitors. In this paper, we present the development of stretchable polyvinyl alcohol (PVA)/carbon nanomaterials(CNM)/polyaniline (PANI) composite with the elongation at break as high as 365% by incorporating stretchability of PVA, electrical conductivity and double-layer capacitance of CNM (CNT and carbon black), and pseudocapacitance of PANI. Based on PVA/CNM/PANI film, a flexible solid-state supercapacitor is fabricated. Supercapacitor not only delivers an outstanding specific capacitance of 284.6 mF cm(-2), but also displays high cycle life. Importantly, a stretchable supercapacitor can also be assembled by two PVA/CNM/PANI film without using carbon cloth and shows no significant energy storage capacity change at different stretching shapes and even repeated stretching/ bending cycles. The results from this study can contribute to the development and fabrication of high stretchable composite and stretchable energy-storage devices.