There exists high peak to average power ratio (PAPR) in optical orthogonal frequency division multiplexing (O-OFDM) system.Traditional tone reservation (TR) method is impro ved to be adapted to current O-OFDM system.A new method combining of improved TR and clippi ng is pr oposed to reduce the influence of clipping noise and decrease the PA PR of OFDM signal at the same time.The proposed method is proved to be with low computational complexity and high technical feasibility.The simulation results show that the in-band noise and out-of-band spectrum are r estrained effectively with TR-clipping under a reasonable value of threshold and reserved subcarriers nu mb er of W.For BER=10－6, as clipping ratio γ decreases from 7dB to 2dB,the nee ded OSNR is reduced from 0.2dB to 7dB compared with th e clipping method.