Abstarct: The aim of this study is the development and characterization a new optical sensor for the determination of trace amounts of lead (ІІ) ions. The 2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol(Br-PADAP), as a chromogenic reagent has been utilized to in the preparing the novel sensing membrane (optode) by the reagent immobilized on the triacethylcellulose membrane. The sensing mechanism is baxsed on the complex formation between Pb (ІІ) and immobilized Br-PADAP at pH=7.5. Increasing in the absorbance of the sensing film at 575 nm was spectrophotometrically measured. Under the optimum conditions and 10, 15, 20 and 25 min response times, calibration curve was linear in the range of 0.50 – 25.0 mg L-1 of Pb (II) and the 3σ limit of detection was found 0.21, 0.12, 0.08 and 0.09 mg L-1, respectively. The sensor can be regenerated by placing the film into a 0.010 M of hydrochloric acid solution for 5 sec for 9 times. The relative standard deviations for five replicate measurements of 2.50, 10.0 and 20.0 mg L-1 of lead (ІІ) in 15 min, was 4.00%, 2.00% and 0.98%, respectively. The sensor showed sufficient repeatability, reproducibility and operational life time of 3 weeks. The optode was successfully used for measuring Pb (II) ions in water samples.