It is a simple and practical method to research nearshore random waves propagation and transformation by the application of the energy balance equation. This method has been used in oceanography and coastal dynamics widely. In this paper, the energy balance equation considering the diffraction effect is used as the control equation to calculate the random wave propagation and transformation. Based on the control equation, a numerical model is established considering comprehensive effects of wave shoaling, refraction, diffraction, reflection and breaking. The random wave propagation and transformation in the harbor basin of Weihai dockyard is simulated using this model. Example results show that the calculated values are in good agreement with the experimental values under the same considered cases. It indicates that the model is practical and reliable to stimulate the nearshore random wave propagation and transformation.