The well-known 8-aminoquinoline framework offers an ideal model for the development of fluorescence-enhanced chemosensors through simple and convenient syntheses. Herein, a novel and simple molecule chemosensor, 5-diethylamino-2-(quinolin-8-yliminomethyl)-phenol (), has been designed by combining an 8-aminoquinoline moiety and a 4-(diethylamino)salicylaldehyde in a single molecule to prove the selectivity and sensitivity for Mg(2+), Zn(2+), and Co(2+) in a dual-channel mode (fluorescence emission and UV/Vis). When binding Mg(2+), not only showed an obvious fluorescence enhancement but also enabled the Mg(2+) detection range over 1.68 ppb. Meanwhile, in mixed solvent media, displayed selectivity for Zn(2+) over other cations by the emission spectrum. It was worth noting that could be a colorimetric sensor for Co(2+) in a semi-aqueous solution by monitoring the absorption spectral behavior and be a colorimetric reagent for sensing and staining of Co(2+) in the cells. The results indicate that can be applied in multianalyte detection.