To evaluate the effect of multipath channel accurately, a modeling method for indoor multipath channel in visible light communication (VLC) system with single light source is proposed. The impulse response of line-of-sight (LOS) and reflection transmission is calculated by recursive methods. Inter-symbol-interference (ISI) is defined after the analysis on the relationship between sampling period of receiver and modulation bandwidth of light emitting diode (LED). Considering the delay time of LOS channel as the modeling origin, the gain of multipath channel is regarded as the sum of all the impulse response in adjacent sampling intervals of the receiver. Because the orthogonal frequency division multiplex (OFDM) technique can effectively resist the ISI, the bit-error-rate (BER) of asymmetrically-clipped optical OFDM (ACO-OFDM) system and direct current-biased optical OFDM (DCO-OFDM) system are derived and the Monte Carlo simulation models are built when the nonlinear clipping noise is considered in indoor multipath channel. The BER performance is studied for different locations of photoelectric detector (PD), semi-angles at half power of LED, fields of view (FOV) of PD, and direct current biases. The simulation results indicate that BER performance is best and the multipath interference is smallest when the PD is located at the center of the room. When PD moves towards the room corner, the BER performance becomes worse and the multipath interference become larger. As the FOV and the semi-angle at half power of LED increase, BER performance degrades due to the increased received power and multipath interference. Moreover, BER performance of DCO-OFDM system is more worse when DC biasing is larger.