Imaging detection and Charge Coupled Device (CCD) detector was adopted in fluorescence detection of DNA capillary electrophoresis in order to decrease the detection width and improve the efficiency and speed of DNA separation. The importance of small detection width for high-speed capillary electrophoresis, especially the separation performed in micro-fluid device, was illustrated according to theoretical calculation based on resolution theory of capillary electrophoresis. The performances of imaging detection and conventional intensity detection were measured and compared. The method of data processing to intensify the DNA band signal of CCD detector was proposed, and verified by simulation. Imaging detection and its data processing method can remarkably decrease the detection width of capillary electrophoresis, and then improve the efficiency and speed of DNA separation.