从Longuet Higgins非线性随机海浪模型出发 ,对波面斜率统计分布进行了理论研究 .结果表明 ,在四阶近似下 ,波面斜率统计分布为截断的Gram Charlier级数 ,截断的项数取决于非线性近似的阶数 ,每一阶近似都对前一阶近似结果有所修正 .如果计及峰度项的非线性影响 ,波面至少应精确至三阶 ,计及偏态的影响则至少应精确至四阶 . Based on the Longuet Higgins nonlinear stochastic ocean wave model, the statistical distribution of wavefront slopes is theoretically studied. The results show that under the fourth-order approximation, the statistical distribution of wavefront slopes is the truncated Gram Charlier series. The number of truncated items depends on the nonlinear approximation Of the order, each approximation of the approximation of the first order have been amended to take into account the non-linear kurtosis term, the wave surface should be accurate to at least three orders, taking into account the effect of bias should be accurate to at least four Order.