The present invention relates to an innovative analyzing and detecting instrument with excellent sensitivity and stability, especially to a present art that realizes the initiation of the dual-purpose instrument in a small inner-casing which combines both ultraviolet-visible and double monochromatic fluorescence dual detector widely used in the high performance liquid chromatography by taking the first to use deuterium lamp as the individual light source of the dual detectors, the individual sample detection cell and the individual electrical circuit, providing two detectors for detecting and analyzing, and emphasizing the advanced automatic gain art adopted in the present invention to make sure the main technical targets of the whole wavelength range are integral, easy to be checked up, and can solve the existing worldwide technical problem of sensitivity-stability exclusion of the two detectors only with the combination of the double techniques in both automatically eliminating noise and reducing drift, so that the excellent technical performance can be achieved.