In order to improve the communication performance of the point-to-po int visible light communication (VLC) system based on discrete multi-tone (DMT) modulation under the different communication distances,a kind of gain-auto-adjusted VLC terminal is designed and implemented based on orthogonal frequency-division multiplexing (OFDM) and 16-phase shift keying (PSK) modulat ion.Gain-auto-adjustment and channel estimation technique are intensively researched.Under the working cond itions with/without using gain-auto-adjustment and with/without using chann el estimation,we test the bit-error-ratio (BER) performance of the VLC system u nder the different communication distances.Experimental results indicate that within the communication distance range of 30－120cm,without using gain-auto-adjustment and channel estimation technique,the BER of the system is as high as 0.1－1．0;by the use of the two techniques,the BER of the system can be dropped to lower than 10－2;also,within the communication distance range of 40－100c m,the BER becomes more constant,whose value is no more than 10－3.This shows that through the use of gain-auto-adjustment and channel estimation,the BER of the system can be decr eased to some extent and the stability of the system can also be improved.