We report an experimental implementation of a continuous variable quantum key distribution (CV-QKD) protocol with discrete modulations together with postselection of the homodyne measurement outcomes. Our experimental system is composed of fiber devices for optical communications. The postprocessing (postselection, error correction and privacy amplification) is performed by a software program. By using this system, we demonstrated CV-QKD over 10km optical fiber using pulsed laser with repetition rate of 10MHz, which is much higher than previous CV-QKD systems.