Hydraulic model tests of wave deformation on the reef with steep forereef slope by using irregular waves were conducted. Two types of the reef topography were inspected. It is confirmed that wave deformation near the reef has very strong nonlinearity near the reef edge. Hydraulic jump at the wave front in times of buckrush and wave breaking in times of uprush coexist at the reef edge. Numerical model based on wave energy balance model developed by Takayama et al. (1991) was modified in order to estimate extreme wave condition inside and outside the reef. The comparison of the numerical simulation result with the experimental one demonstrates that Takayama's model improved in this study provides very good agreement with the experimental data.