In this paper, 2-(2_-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer(ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe3+ sensitive optochemical sensor.The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe3+ was attributed to the blocking of ESIPT reactions of HPQ andquenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. Thesensor shows a linear response toward Fe3+ in the concentration range of 7.1×10−7 M to 1.4×10−4M with a limit of detection of 8.0×10−8 M,and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe3+ over a large number of cations such as alkali, alkaline earth andtransitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples withsatisfactory results.