确定渗透参数的概率分布是堤防渗透稳定可靠性分析的基础。阐述了土体渗透系数和临界水力比降的概率分布研究概况。通过分布参数的极大似然估计和A?D法分布拟合检验，分析了堤防粉质粘土和粉质壤土的渗透系数概率分布；基于太沙基公式，将土粒相对密度和孔隙比作为随机变量，推导了临界水力比降的概率密度函数。分析表明，渗透系数的概率分布符合对数正态分布，临界比降的概率分布为近似正态分布。

The determination of probability distribution of seepage parameters is a basis of reliability analysis of levee seepage stability. The research development of soil permeability and critical hydraulic gradient is presented. The probability distribution of levee soil permeability is analyzed by maximum likelihood estimation of distribution parameters and A-D test method for distribution fitting. On the basis of Terzaghi formula of flowing soil, the probability density function of critical hydraulic gradient is derived with soil relative density and void ratio as random variables. Results show that the distributions of the permeability of silty clay and silty loam are both subject to lognormal distribution, the soil critical hydraulic gradient obeys approximately normal distribution.