Abstract: In this paper, the spatial variability of solute transport velocity is analyzed based on the unsaturated solute transport experiment in a field. The lognormal distribution function of the velocity and then the effective dispersivity are obtained. The mean concentration and variance are calculated by using convective equation and convective-dispersive equation with the resulted stochastic velocity and the classical convective-dispersive equation. The calculated result is in fairly agreement with the experimental data. It is shown that the concentration variance is proportional to concentration gradient and inverse proportional to the local dispersivitv. The maximum concentration variance is near the concentration front.