Indoor visible light communication (VLC) systems are usually designed based on asymmetric clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and DC biased optical OFDM (DCO-OFDM). These system models usually use CP, channel equalization and carrier multiplexing to solve the problems of channel interference and multi-user multiplexing. But these are at the expense of effectiveness. Non-orthogonal multiple access (NOMA) improves spectrum utilization by sub-carrier multiplexing in power domain, and uses serial interference cancellation (SIC) for multi-user signal processing. It is an effective method to balance communication reliability and effectivity. An indoor VLC system based on NOMA was proposed, and a VLC signal transmission and channel gain model based on NOMA-DCO-OFDM were established. According to channel gain of multi-user, the power allocation of NOMA was carried out to realize the multiplexing in power domain and improve the capacity of system and the communication rate. SIC was used to demodulate the multi-user signals one by one according to the power allocation algorithm to reduce channel interference and improve the reliability of the system. Theoretical analysis and experimental verification show that the communication rate of the system reaches 6.8×10⁷ bit·s^-1, the combined rate is not significantly affected by the number of users, and the communication efficiency is significantly improved. For 2 users, when BER is 10^-4, user 1 has about 5.2 dB performance improvement, user 2 has about 2.3 dB performance improvement, the communication reliability is also improved.