High Peak to Average Power Ratio(PAPR) is one of the major disadvantages of the Visible Light Communication(VLC) Orthogonal Frequency Division Multiplexing(OFDM) system as it can cause signal distortion. A Selective Mapping(SLM) method is introduced in order to reduce the PAPR of OFDM signal in VLC system, which is modified to suit the demand that the signals must be positive and real. A method combining the Discrete-Fourier-Transform Spread(DFTS) and SLM is proposed to reduce the PAPR in VLC OFDM system further. The simulation results show that，comparing with the original signal，DFTS or SLM method used alone, the DFT-S-SLM method has the best PAPR performance at the cost of a certain increase of system complexity.