Physical and chemical properties for sieving polymer are essential for capillary polymer electrophoresis.The "mesh size" or "pore size" of the sieving polymer filled into capillary functions as the carrier molecules and a sample polyelectrolytes are separated in order to their molecular weight.The mechanism of the polyelectrolytes migration through the sieving polymer solution has been explained by theoretical models, such as Ogston, reptation and the biased reptation models, which are analogous to the DNA sieving mechanisms.In capillary polymer electrophoresis, the migration of polyelectrolytes is assumed to be due to a physical sieving mechanism, thus, the separation performance of polyelectrolytes is dominated by the "mesh size" or "pore size" of the sieving polymer networks.