The embodiment of the invention provides a multi-core optical fiber communication system and a multi-core optical fiber communication method. The system comprises a ring backbone network, a first multi-core optical fiber and at least one optical network unit. The ring backbone network comprises a control center, a downlink ring network channel and an uplink ring network channel. The first multi-core optical fiber comprises a first downlink channel core group and a first uplink channel core group. The downlink ring channel of the ring backbone network is connected with the first downlink channel core group of the first multi-core optical fiber; the uplink ring network channel of the ring backbone network is connected with the first uplink channel core group of the first multi-core optical fiber; the ring backbone network is connected with the optical network unit through the first multi-core optical fiber. The invention realizes the purpose of obtaining a multiplexable multi-core optical fiber transmission scheme and reducing the cost of an optical network unit.