The wave breaking positions of the island reefs were tested by a series of wave flume model tests.In the experiment,the reef topography was generalized to the model connecting the steep slope to the horizontal platform.The locations of the wave breaking under 3 kinds of steep slopes (11.5,13 and 15) and 3 relative water depths (0.1,0.17 and 0.24) were studied.The results show that the relative position of wave breaking is related to the number of Irribarren,the relative water depth of the reef flat and the fore-reef slope.The breaking position moves toward the shore with the increasing of Irribarren number and relative water depth,but toward the sea side with the steepness of the slope.Finally,the calculation method of wave breaking position was also given in this paper.