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A novel ionic polymer metal composite (IPMC) actuator based on partially fluorinated ionomer composed of polyvinylidene fluoride (PVDF) and perchlorate is successfully developed. The PVDF-base films are prepared by solution casting, followed by electroding with gold (Au). Unlike other commercial Nafion-base IPMCs, the PVDF film doped with 15 wt.% Cobalt perchlorate (Cop) is the first one of electroactive polymers which show large cathode deformation. 3.5V DC is lowest drive voltage and best electromechanical behavior is shown under 4V DC. Over 250° of bending angle and less than 30s of response time are observed. A CCD camera records the deformation history, Tracker software is used to analyze video and bending angle can be calculated by Newton method. In high humidity (43%), PVDF-CoP film shows fast cathode deformation, followed by positive back relaxation when the DC electric field still applied on. While the PVDF-base IPMC doped with 7.5 wt.% lithium perchlorate (Lip) display anode deformation without any back relaxation. It means that the different cations can be tailored to obtain a desired actuation response. The actuation process depends on size difference between cation and anions. It is discovered that back relaxation will disappear when humidity down to 33%. If humidity low enough (23%), samples show maximum bending without back relaxation. We have reason to believe that hydration reaction of cations could largen the diameter of hydrated cations. It leads to decrease the size difference between hydrated cations and anions.