Abstract: A mathematical model describing the intraparticle flow contributed by Poiseuille flow and electroosmosis in the electrochromatography was established, which showed that the contribution of electroosmotic flux became dominant when the pore diameter to particle diameter decreased. A new concept in terms of effective diffusivity was proposed to quantify the electroosmosis enhanced intraparticle mass transport. The height equivalent of a theoretical plate (HETP) of electrochromatography was calculated as function of the effective diffusivity. The effects of Poiseuille flow and electroosmosis on the magnitude of HETP was investigated, respectively. It was shown that enhancement of intraparticle mass transport by Poiseuille flow, as shown by the reduction of the magnitude of HETP, could only obtained for those large pore particles characterized by pore diameter over 500 nm. While the introduction of intraparticle electroosmosis led to the increase in the effective diffusivity and the reduction of the HETP, both of which were dependent on electric field strength and were independent of pore diameter. Prediction of the breakthrough behavior of electrochromatography was attempted using the model developed by Yoshida. The predicted breakthrough curve as a function of the electric field strength was in good consistency with those experimental results obtained in different electrochromatography systems. This demonstrated the validity of the theoretical results obtained by the present study.