In this paper, an adaptive transmission system with a special multiplex core for the optical wireless communication (OWC) is proposed, which can adjust the transmission mode automatically according to the channel status information (CSI). The atmosphere channel is a time-variable channel in which link performance could be affected by weather and scintillation. Adaptive transmission (AT) technique is introduced to solve the problem. Certain CSI that can evaluate the quality of atmosphere channel should be chosen to vary the transmission mode of OWC terminals in order to confront bad weather condition and maximize average throughput of transceiver. Considering that the system can choose suitable communication bit-rate, transmission power and with or without channel coding and some other flexible features, the special multiplex core has been used to guarantee the data to be multiplexed correctly. The data can be packaged into fixed length frame with the channel ID. Data stream is buffered by Dual-port FIFO with multi-clock feature and multiplexed by a smart controller with a certain algorithm. The special system structure makes it possible to replace the data interface without any change of the rest parts.