This paper adopted the adaptive Metropolis algorithm of Markov chain Monte Carlo approach (AM-MCMC) to estimate the parameters of van Genuchten model, which describes the soil water characteristic curve. The posterior statistics of the van Genuchten model parameters were obtained to estimated the model uncertainty. It was found that the distribution of the posterior means and variances of the model parameters could be obtained. Confidence intervals of the model parameters could be ascertained. It was proved effective and novel in solving van Genuchten equation with this algorithm.