A simple acylhydrazone derivative 4-chloro-N′-(pyridin-2-ylmethylene) benzo- hydrazide (CPBH) has been designed to be a fluorescence probe for Al3+. The limit of dection for Al3+ is 0.2 μM (5.4 ppb). The CPBH and Al3+ form a 2:1 coordination complex. The binding equilibrium constant K is about 4.69 × 104 M−1 and 3.68 × 104 M−1 based on the data from absorption and emission spectra, respectively.