An amide-linked 2,6-bis{[(2-hydroxy-5-tert-butylbenzyl)(pyridyl-2-methyl)-amino]-methyl}-4-methylphenol-ruthenium(Ⅱ) tris(bipyridine)2PF6− complex, 1, was first used to recognize Co(Ⅱ) in EtOH/H2O (1:1, v/v) solution, with the ruthenium(Ⅱ) tris(bipyridine) moiety selected asa fluorophore and the multi-substituted phenol unit chosen as a receptor. The fluorescence quenching of 1 was attributed to the formation of aninclusion complex between multi-substituted phenol unit and Co(Ⅱ) by 1:1 complex ratio (K=2.5×105), which has been utilized as the basis of thefabrication of the Co(Ⅱ)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Co(Ⅱ)-sensitive chemosensorwere investigated. The sensor can be applied to the quantification of Co(Ⅱ) with a linear range covering from 1.0×10−7 to 5.0×10−5M and adetection limit of 5×10−8 M. The experiment results show that the response behavior of 1 to Co(Ⅱ) is pH-independent in medium condition (pH4.5-9.5) and show excellent selectivity for Co(Ⅱ) over transition metal cations except Cu(Ⅱ). The chemosensor has been used for determination ofCo(Ⅱ) in water samples.