The Fractionally Spaced Equalization (FSE) technology is investigated to mitigate the effects of Inter-symbol Interference (ISI) on the indoor Visible Light Communication (VLC) systems. Based on the propagation properties and signal modulation characteristics of indoor VLC systems, a link model for the indoor VLC communications is described, then the FSE method is proposed by using the link model. Furthermore, based on the minimum Mean Square Error (MSE) criterion, the FSE is optimized. Finally, the performance of the proposed FSE theory is evaluated by computer simulation. Experimental results indicate that the performance of T/2-fractionally spaced equalizer has improved 1-2 dB than that of the symbol interval equalizer in the same Bit Error Ratio(BER). It can eliminate the effects of the ISI induced by the multipath effectively, and can improve the reliability of signal transmission.