Abstract: Fiber-like MnO₂ was synthesized by liquid -phase reaction. By adding PAM modifier tothe agar, a new type of supercapacitor membrane was prepared in order to improve the general perfor-mance of agar. When the amount of PAM is 800ppm in the modified agar, the absorbency reaches400.1%, the rate of rention reaches 335.1%, the discharge capacity is 23.4F/cm³ in the MnO₂/Csupercapacitor. Other properties, such as cycle life, ESR and toughness are also improved.