The invention relates to a discrete channel access method based on CMA competition and TDMA reservation. The method comprises the following steps: step one, computing time slot number needing to be occupied by a computing node according to a channel usage condition and a data cache queue; step two, enabling the node meeting the condition to successfully win the node transmission data of the channel resource through the CSMA competition channel when the channel is idle; step three; successfully transmitting node reserved time slot of the data; and step four, releasing the time slot when the channel load exceeds the threshold, or the reserved node cache queue data size is 0. Through the method disclosed by the invention, the conflict caused by access and time slot adjusting can be reduced, and the system throughput is improved.