A new kind of soluble poly(p-phenylenevinylene) (PPV) derivative containing free olefinic bonds at the side chain is prepared and studied by electrochemical measurement. The electrochemical investigations reveal that the free olefinic bonds in these polymers are electroactive; a new redox reaction occurs prior to the oxidation of PPV backbone in the cyclic voltammetry. The lower oxidation potential of the olefinic bonds hints that it is possible for these olefinic bonds to react with oxygen, which is desirable to remove the harmful oxygen in the light-emitting polymer devices. The merits and possibility of such polymers containing olefinic bonds in the fabrication of the light-emitting devices are discussed.