The SIEA 28 kDa component of Schistosoma japonicum purified by gel electrophoresis was isolated and purified further by ion exchange high performance liquid chromatography (HPLC) and then its pI was measured by thin-layer PAG-IEF. After purified by HPLC, its component took the appearance of a symmetric smooth chromatography curve with a single peak both in 220 nm and 280 nm wavelength. The curve of chromatography elusion verse its activity was also symmetric and single-peaked. The result shows that SIEA 28 kDa component is probably a single molecule and its pI is ranged from 5 to 7.