A simple "off-on" fluorescent chemosensor with high selectivity to zinc ions based on 1,10-phenanthro- line receptor dipyrido[3,2-d:2′,3′-f]quinoxaline(L) was investigated. The selectivity response of receptor L to zinc ion was demonstrated by UV-Vis absorption and fluorescence spectroscopies in DMF buffer solution. The experiment results show that the fluorescent chemosensor L exhibits the optimum response behavior to Zn2+ in the range of pH 8.0―9.0 and shows excellent selectivity to Zn2+ over other cations tested.