In conventional OFDM system,an OFDM symbol will exceeds its guard interval (GI) and seriously interfere with its neighboring symbols when channel characteristic is unsatisfactory.This will cause intersymbol interference (ISI) and intercarrier interference (ICI).In highspeed incoherent optical OFDM communication system,a novel time domain reshuffling method for mitigating ISI and ICI based on DCOOFDM was proposed.This scheme utilized the properties of Fourier Transform.By simple preprocessing subcarrier channels in frequncy domain,sampling sequence of a DCOOFDM symbol in time domain was exchanged interactively.Thus signal energy was centralized in the central part of a symbol.Numerical simulation indicates that ISI and ICI is significantly reduced and system BER performance is improved effectively due to signal surpassing the GI.In optical OFDM systems with insufficient GI for the popurse of higher information transmission efficiency,the reshuffling scheme also has a great value.