Based on the carbon fiber cylinder solid phase extraction technology, a system was researched, which can be used to complete step elution, separation and continuous/selective injection for different polar compounds. The process was realized through the valve switching and more than one peristaltic pump controlled by single chip microcomputer. The connector between liquid chromatography (LC) and UV-detector is also available in this paper. The experimental results show that, this combined system meet the requirement of QA/QC in the aspect of simple operation, high precision and repeatability. It can be widely used in online analysis of different polar compounds with liquid chromatography in the fields of environment analysis, drug analysis, life science, etc.