Abstract: There are many factors causing contamination in batching. The basic factor of them is the scattering behavior of medium, that is to say, convection and diffusion. The process of contamination between two products is two-D process of convective diffusion, as well as axial elongation & radial diffusion. The axial elongation is caused by un-uniform velocity on the section of pipe flow and diffusion is caused by concentration gradient. We have learned through analysis that the higher Reynolds number is, the nearer result from One-D contaminating theory closes to solution getting from Two-D contaminating theory, so as the lower Reynolds number is, the greater error from One-D contaminating theory is. And further more, under the state of laminar flow, One-D contaminating theory is untenable. So in design and operation for batching transportation, it is required higher Reynolds number and strict turbulence flow. The difference between these two results are getting smaller along with increase of Reynolds number.