Based on the mild-slope equation, a slowly-varying factor has been introduced to derive a new governing equation (Jen,1993 ; Wu,1995) by Galerkin method of the finite element approach. An item is added to include breaking wave energy dissipation in the governing equation. It is intended to simulate the nearshore wave field with combined refraction, the reflection, the diffraction and the breaking wave phenomenon. Wave transformations with wave-breaking energy dissipation across the surf zone are solved through iterative method. Present numerical result are then compared with experimented measurement (Maruyama, 1984) in a case of offshore beakwater. Reasonable agreement is observed.