Continuous counteracting chromatographic electrophoresis(CACE) concentrates target-protein continuously to accumulation zone between exclusive and inclusive zones with a separation column by using opposing electrical and flow fields. The mathematical models for three zones of a continuous CAGE column are proposed. An on - line monitor system is constructed to monitor in situ the concentration of target protein and its variation within the accumulating zone. Experiments are made with hemoglobin and cytochrome C by using two sets of continuous CACE apparatus.