Due to the special vehicle′s narrow space, lighting layout is limited and the difficulty is increased. An optimal scheme of lighting layout was proposed based on optical power evenly distribution principle. Inter symbol interference model caused by the multipath dispersion from the reflection of floor in vehicle was built. The influence of multipath propagation delay on optical communication system was investigated. The relevant characteristic between the root mean square delay spread and max data rate was analyzed. Meanwhile, the Bit Error Rate(BER) was calculated by the simulation software. Simulation experiments proved that the optimizing layout scheme was valid as follows: the received optical power ranged from -0.73 dBm to 0.56 dBm in 2 m×2 m×1.5 m space size, uniform illumination rate was 80.5%, the average Signal Noise Ratio(SNR) was 20.92 dB. Moreover, the max data rate can be improved from 107.8 Mbps to 373.3 Mbps OOK at a BER of up to 1.47×10-6, which meet the international illumination standards and the actual data communication in a special vehicle.