Model tests have been carried out in order to make clear the characteristics of wave transformation, elevation of mean water level or surf beats over a reef with water depth of 0m to 5.0m and the length of 200m to 2,000m.
　The model tests drew the following characteristics of waves on the reef:
1) Wave heights increase to maximum height on the slope in front of the reef, and then decay rapidly on the slope and the reef front area. They seem to approach to constant values as the waves travel on the reef.
2) Between two wave trains same wave steepness, a train with larger ratio of water depth on the reef to its significant wave height in deep water decays its heights on the reef less than the other.
3) Between two wave trains with the same ratio, a train with smaller wave steepness decreases its height less than the other.
4) The mean water level begins to increase on the slope in front of the reef, and continues to become higher even on the reef. However, after it reaches the maximum, it decreases gradualy.
　Based on the adove characteristics, the empilical formulas are derived on the purpose of the estimation of the wave transformation and the mean water elevation. In the results of the comparison between the calculated values and the experimental ones, the formulas are verified to be applicable to the estimation of wave heights or the mean water level on the reef.