Here we reported flexible aerogel electrodes for supercapacitors fabricated by freeze-drying combining a cold-press process cellulose nanofibers (CNFs), multi-walled carbon nanotubes (MWCNTs) and polyaniline (PANI) composite system after polymerized polyaniline onto the surface of the cellulose nanofibers and carbon nanotubes by in situ polymerization method. Scanning electron microscope images showed that PANI well coated on the surface of the CNFs and MWCNTs forming a three dimensional conductive network structure. PANI as binder firmly combining each other together and cross-sectional loose structure lead to a small charge transfer resistance (1.24Ω). Due to the 3D porous structure of the aerogel electrodes, a high specific capacitance of 791.13F/g was obtained at 0.2A/g. Furthermore, the aerogel electrodes also showed excellent redox reversibility and cycling stability. The low cost, super light-weight, high-performance, and environmental friendliness aerogel electrodes may have a promising application for the flexible supercapacitors.