The invention discloses a communication system of a DC grid. The DC grid comprises DC grid control equipment and N sets of converter station control equipment. The communication system comprises n transmission channels, wherein one end of each of the n transmission channels is set at the DC grid control equipment, and the other end is connected with the corresponding converter station control equipment, wherein n <= N; and the transmission channels can adopt optical fibers for transmitting data to be exchanged, the converter station control equipment is only in communication and connection with the DC grid control equipment, and the data to be exchanged among the converter station control equipment is forwarded by means of the DC grid control equipment. The communication system achieves the purposes of reducing communication and bandwidth resource consumption through designing communication between stations, and can be more suitable for the access of other converter stations in the later period. The invention further discloses a communication method of the DC grid.