A reasonable free space optical orthogonal frequency division multiplexing (FSO-OFDM) experimental system model is set up according to the principle of orthogonal frequency division multiplexing (OFDM). The performance of this scheme is simulated under various channel conditions. And the impact of channel noise on OFDM modulation constellation is tested experimentally, which provides an experimental basis for FSO-OFDM. The result shows that FSO-OFDM system has better performance to restrain inter-symbol interference, and its error rate is lower than that of the single carrier modulation system.