A wide variety of molecular probes have been developed for real-time analysis, but most of organic fluorophores possess small Stokes shifts and self-absorption or inner filter effect that could not be avoided. In this study, a new dicyanoisophorone-based derivative (E)-O-(4-(2-(3-(dicyanomethylene)-5,5-dimethylcyclohex-1-en-1-yl)vinyl)phenyl)diphenylphosphinothioate (λex=405 nm, λem=551 nm, denoted as ICM-S) with strong push-pull electron effect has been afforded and it exhibits red shift for absorption from 407 nm to 426 nm with distinct color change from pale yellow to deep yellow upon exposure to Hg2+. Moreover, an easily distinguishable fluorescence color change follows the route from green, yellow to red in the presence of Hg2+over the range of 0-90 μmol/L (detection limit=137 nmol/L) can be observed by the naked eye under a UV lamp irradiation. Chlorodiphenylphosphine and sublimed-sulfur are incorporated as responsive sites and P-O bond has been cleaved upon the addition of mercury ions. During the recognition process, such dicyanoisophorone dye (ICM-S) has been evolved to 2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (ICM-OH). Clear evidences in the chemical processes can be identified via single crystal X-ray diffraction, spectroscopic analysis, photophysical studies and titration experiments. With the aim of exploring its potential in biological systems, its in vitro responses to Hg2+have been evaluated in 293 Tcells and the effectiveness in zebrafish model has also been verified.