A porous core electroosmosis pump was studied and improved in accordance with the electroosmosis theory. Hexamethylene tetraamine (HMTA) was used as the additive of pump carrier solution to improve the flow rate stability and delivery efficiency. The influences of the electric field strength, porous core dimension and acetonitrile concentration of carrier solution on the pump flow rate and output pressure were investigated in detail. The improved electroosmosis pump can provide not only steady flow rate and large flow range, but also moderate output pressure. With the pump carrier solution of 0.5mmol/L HMTA and the working voltage of 4950V, the pump output pressure, flow rate and delivery efficiency achieved 1.1MPa, 1.3mL/min and 3.2mL/(minmA), respectively. The pump can be employed for mobile phase delivery in the reversed-phase chromatographic separation of monolithic silica columns.