In indoor Visible Light Communication (VLC) system, the data carried by Light-emitting diode (LED) light is transmitted through the optical channel through multipath dispersion. Different indoor reflective surfaces are incorporated into the model through MATLAB simulation modeling, and the channel impulse response algorithm is proposed. Direct Current biased Optical Vector Coding (DCO-VC) technology is introduced in the system. The DCO-VC system uses M-ary pulse amplitude modulation (M-PAM) as modulation scheme, to adjust the system data transmission efficiency and accuracy. Intercell interference is introduced into the simulation model. Studies have shown that the higher the modulation parameter is, the higher the data transmission efficiency of the system is. When the modulation parameters are lower, the transmission efficiency of the system is relatively reduced, but the transmission accuracy is higher and the system can still output effectively in the presence of inter-cell interference. In real application, when the system signal-to-noise(SNR) ratio is lower than 35dB, 2PAM or 4PAM modulation should be applied to ensure the transmission accuracy. When the SNR ratio exceeds 40dB, use the 32PAM modulation to increase the transmission rate.