To improve the data transmission rate of the conventional point-to-point single input single output (SISO)visible light communication system, a multiple input multiple output (MIMO) visible light communication system is proposed. Considering the complexity of the receiver system, multiple input single output (MISO) visible light com-munication systems have attracted attention. This paper studies the MISO visible light communication system based on pulse amplitude modulation (PAM), and experimentally proves the advantages of this system in specific scenes. In addition, there are non-linear effects for key devices such as LED light sources and power amplifiers in visible light communication systems. Based on 2×1 MISO visible light communication system, this paper reports a novel equal probability coding mapping scheme for high-order PAM signals with two low-order PAM signals superposition in the optical domain. The system verification is performed through a net data-rate of 700 Mb/s transmission experiment through a red chip of RGB-LED, which proves the feasibility and superiority of this scheme in practice.