Mercury in its lipophilic and inorganic form is a major threat to the environment and to human health. It is therefore highly necessary to develop a chemosensor for mercury detection. A novel fluorescent probe for mercury, 7-(vinyloxy)-3H-phenoxazin-3-one has been designed and synthesized by anchoring resorufin (helping as a fluorophore ) with vinylic ether moiety. In present work we have designed a fluorescence strategy based on the π-electrophilicity. The Probe is essentially nonfluorescent which upon reaction with Hg(II) undergoesoxymercuration of vinylic doublebond followed by cleavage, complemented by the generation of strong fluorescence to detect traces of mercury in biological samples. The resorufin based probe responds selectively to mercury species, while reluctant or little responsive toward other analyte metal ions. Significant colorimetric and fluorescence change from colourless to pink through the anchoring and unanchoring process is being observed.