In order to verify the stability of rubble-mound breakwater of a harbor, the paper established physical model and obtained wave height distribution within engineering area by using the height wave acquisition device. Visual observation method is used to get the instability number of slope breakwater armor stones of different areas and also to describe the situation of wave overtopping. The results show that when wave incomes obliquely, the stability is better than wave incomes normally, the dam body satisfies the requirement of stability. The physical model reflected the fact well. According to the experimental results, the original program was optimized and also met the requirement of stability.