Abstract: A fully nonlinear Boussinesq equation is applied and verified against experimental data. The transformation of wave nonlinear parameters (i.e., wave asymmetry and wave skewness) for the irregular wave transformation over a gentle submerged bar is investigated with this model. Wave asymmetry changes from negative values to positive values, and reaches the minimum and the maximum in the front and back crest of the submerged bar, respectively. Wave skewness increases in the upslope region and reaches the maximum on the crest of the submerged bar and reduces to zero in the downslope region. The damaged location at the submerged bar are probably affected by wave erosion, especially for those waves with extreme values. Based on several typical position of wave trains and their spectra, the reason of changes of wave nonlinear parameters is analyzed. The empirical formulas are fitted and analyzed for the variation of wave asymmetry, skewness with Ursell number in the upslope region and downslope region.