Several sets of S4 direction-wave-current-tide meters have been deployed on the coral-reef fiat of fongshu Reef in the sea area of Nansha Islands. Based on the observationat sea wave data, the attenuation, hara, teristics of the waves propagating on the coral reef flat, the bottom friction coefficeients and the transfer of wave, energy are discussed it, the paper. The results show that, in the relative depths of 0.0613～0.0867, the wave height attenuation per unit distance of wave propagation is 22.09%～46.56%, with an average of 31.35%; the wave energy attenuation coefficient, 33.74%～53.22%, with an average of 43.61%. The average of the bottom friction coefficients on the eoral-reef flat is 0.1346, which is about 10 times that on the sand or silt bottom. In the course of propagation an the reef tlat, the waves sustain more loss in high frequency than in tow frequency and the spectral energy, transfers to, the low frequency. These results may be used for reference in island and reef engineering.