High performance solar-blind photodetectors have been fabricated from diamond wafers. The peak responsivity is 13.0 A/W at 222 nm with a dark current of 0.93 nA under 60 V bias. The rise and decay times of the photodetector are about 1.3 µs and 203 µs, respectively. The responsivity and response time of the device are both among the best values ever reported for diamond-based photodetectors. A solar-blind optical communication system has been constructed by employing the diamond photodetector as a signal receiver for the first time. Benefiting from the high spectral selectivity of the diamond photodetector, the communication system has excellent anti-interference ability. The results reported in this paper may pave the way for the future application of diamond-based solar-blind photodetectors in confidential communications.