Abstract: With the rapid development of global economy, the depletion of fossil fuels, and the severe environmental pollution, new electrochemical energy storage technologies are in urgent need. In recent years, supercapacitors have attracted extensive attention due to their advantages of high power density, long cycle life, wide working temperature window, and excellent cycling stability. Unfortunately, traditional supercapacitor devices are big and heavy, complicated to manufacture, and most of the time undegradable, and therefore cannot achieve sustainable development goals of the society. In this content, it is imperative to develop an innovative type of flexible and environmental friendly supercapacitor. Polyaniline-polylactic acid (PANI-PLA) biodegradable flexible supercapacitor electrode was prepared by in situ chemical polymerization method utilizing polylactic acid (PLA) film as the substrate. SEM, FTIR, and UV-Vis were performed to characterize the morphology and chemical structure of the electrode. The electrochemical tests show that under the three-electrode system, the areal specific capacitance of PANI-PLA can reach 5.00 mF·cm ⁻² (@0.10 mA·cm ⁻²). Under the two-electrode system employing polyvinyl alcohol/sulfuric acid (PVA/H ₂SO ₄) as the gel electrolyte, the symmetric PANI-PLA//PANI-PLA solid supercapacitor delivers an areal capacitance of 0.20 mF·cm ⁻², a power density of 3.60 μW·cm ⁻², and a corresponding energy density of 0.02 μW·h·cm ⁻² (@0.004 mA·cm ⁻²). The asymmetric solid supercapacitor consisting of polyaniline grown on stainless steel (PANI-SS) and PANI-PLA delivers an areal capacitance of 23.33 mF·cm ⁻², a power density of 30.09 μW·cm ⁻², and a corresponding energy density of 1.17 μW·h·cm ⁻² (@0.05 mA·cm ⁻²).