In order to ensure stable, correct and real-time high-speed transmission of indoor visible light communication (VLC), the key modulation and demodulation technologies of orthogonal frequency division multiplexing (OFDM) are studied in this paper. The time-domain synchronization, frequency synchronization and channel equalization of receiver are analyzed and optimized by utilizing short and long training preamble. Moreover, field programmable gate array (FPGA) development board (Xilinx Kintex-7) and Verilog hardware description language are used to realize the design of proposed OFDM-VLC system. Simulation and experiment both verify the feasibility of the hardware designs of this system. The proposed OFDM-based VLC system can process signal in real-time, which can be used in actual VLC application systems.