A VDB transmitter in Local Area Augmentation System is a kind of special TDMA-based data communication equipment for aviation. The paper researches the composition and data processing of VDB, analyzes theoretically how to improve performance of VDB communication system by using FEC RS (255,249). In addition, the combination of signal generator and computer is used to build an experiment of VDB transmitter for observing the VDB transmitting signals, together with simulation system of VDB communication by MATLAB. The simulation shows that FEC coding can improve the performance of VDB communication system.