Polyaniline (PANI) is considered as an attractive electrode material in energy storage devices. Here, self-supported porous conducing PANI fibrous network is in-situ deposited on carbon paper (CP) via a facile electropolymerization method for solid-state supercapacitor. We also explicate the possible growth mechanism of nanofiber network based on the morphology evolution. Combined with high specific surface area (42.2-96.3 m(2) g(-1)), controllable loading capacity (10 mu g cm(-2) cycle(-1)) and superior conductivity (1.13-1.98 S cm(-1)), the composite electrodes are further proved with FTIR, Raman, XPS and UV-Vis spectra. The capacitance performances are systematically investigated via cyclic voltammetry, galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. As-prepared CP/PANI-80 hybrid electrode exhibits mass capacitance of 455.1 F g(-1) under 0.5 A g(-1) with pseudo-capacitive contribution -58.4%. Meanwhile, the gravimetric capacitances of composite electrodes follow a decline trend with increase of loading capacity as the effective utilization rate and specific surface area of active PANI. Then, the solid-state supercapacitor device assembled delivers mass capacitance of 149.3 F g(-1) and presents admirable energy density of 13.3 Wh kg(-1) with power density 80 W kg(-1) in PVA/H2SO4 electrolyte. Moreover, solid-state device exhibits favorable self-discharge behavior with low leakage current as small as 27.5 mu A, distinct long time cycling stability with capacitance retention of 81.6% after 4000 continuous cycles. Above encouraging results could illustrate the great promise of this method and tremendous potential of PANI fibrous network electrodes in solid-state energy-storage systems.