The effect of convective velocity in the packed column is presented. When an electric field is applied, the conformation of polyelectrolyte quickly orients in the field direction. The convective velocity of polyelectrolyte inside a porous gel particle is accelerated. The dependence of the transport in the gel particle upon field intensity and molecular size aids in understanding the transport of polyelectrolyte in the packed column. To date, few dynamic studies of polyelectrolyte in a porous gel particle have been attempted for the separation of polyelectrolyte in the packed column. Convective-diffusive transport of DNA is analyzed by physical properties measured experimentally, such as the diffusion coefficient, the electrophoretic mobility and the gel porosity. The purpose of this study is to show how the variation of physicochemical properties in the gel particle affects the separation of DNA from a mixture in the packed column. A theoretical model using the characteristic method is used to calculate the separation point in the packed column.