A new Rhodamine B hydrazide hydrazone 1 has been synthesized and investigated as a colorimetric and fluorescent "off-on" sensor for the recognition of $Cu^{2+}$ in $CH_3CN/H_2O$ (1:1, v/v, HEPES 10 mM, pH = 7.0) solution. Sensor 1 displayed highly selective, sensitive and rapid recognition behavior toward $Cu^{2+}$ among a range of biologically and environmentally important metal ions. Sensor 1 bind $Cu^{2+}$ via a 1:1 stoichiometry with an association constant of $1.92{ imes}10^6;M^{-1}$, and the detection limit is evaluated to be $7.96{ imes}10^{-8};M$. The $Cu^{2+}$ recognition event is reversible and is barely interfered by other coexisting metal ions.