An electro-optic polymer waveguide modulator based on both Pockels and Kerr effects has been demonstrated. A conjugated polymer, poly (9,9-dioctyl-2,7-fluorene-co-benzo [c][1,2,5]thiadiazole-co-9-hexyl-3,6-carbazole), which has the delocalization of p-electrons and a push-pull structure along the main conjugated chain, exhibits the Pockels effect and still maintains the Kerr effect after corona-poling. By applying a direct current (DC) bias, the optical output of the modulator is roughly linearly to a modulation voltage, and the modulation depth is improved with the DC bias at fixed modulation voltage. The proposed modulator achieves a 2.18% modulation depth with 5 V p-p modulation triangular voltage and 90 V DC bias at 100 kHz by employing both the Pockels effect and Kerr effect.