The unperturbed separatrix crossings driven by a single wave are discussed. The separa-trix crossings are followed by a mixing process, and a small-scale structure occurs in the distribution function in h-ψ plane. The separatrix crossings form a convective process in h-ψ plane, and the convective flux and the net flux are calculated. The separatrix crossings are accompanied by a radial flux, which is composed of a directional flux and a diffusional flux, both of them are calculated.