Experiments on the interaction forces between waves and seawalls on reefs were conducted in the large wave flume of Tianjin Research Institute of Water Transport Engineering. Wave forces, including the horizontal and uplift pressure on seawalls, were measured at different water levels and wave conditions. The forces values were compared with those obtained by formulas in Hydrographic code for ports and waterways. The experimental results show that wave forces on seawalls were controlled by wave setup, wave height and wave induced flow after breaking. Horizontal pressure had a rectangular distribution while uplift pressure had a triangular distribution. The experimental values were less than those obtained by formulas using wave conditions in deep water. Correction coefficients based on the relative distance of seawalls and reef edge as well we the relative water depth on reefs were proposed. It has been demonstrated that values of the correction formula were in good agreement with the experimental results.