Jet diffusion in plunge pool is one of the research topics of many researchers. Most of these researches were done experimentally and few of them were done numerically. In this study, jet diffusion in plunge pool is simulated by using FLOW3D software. Result of models show that this software has a high capability in predicting of jet diffusion characteristics such as velocity profiles and diffusion angles in free jet and impinging regions. The height of impinging region in numerical model is very close to experimental results. Numerical model results have shown that angles of jet diffusion i.e. outer spread angle and inner core decay angle are 5 to 11° and 9 to 12°, respectively. Numerical model predicts the normalized mean pressure (Cp) equal to 1.0 in the plunge pool floor when core jet meets the plunge pool floor whereas this parameter is less than 1.0 in the experimental model because of air entrainment to plunge pool. Moreover, normalized pressure profiles in the plunge pool floor has similar results with experimental cases.