The chromogenic reaction of Al (III) with morin was studied in the presence of cationic surfactant cetyltrimethylammonium bromide(CTMAB), Al (III) was capable of reacting with morin to form a stable yellow complex in 0.17 mol l-1 glacial acetic acid media. The complex had a 1∶2 molar ratio for Al (III) and morin . In the presence of cationic surfactant CTMAB, the sensitivity of chromogenic reaction was largely improved. At the maximum absorption wavelength of 425nm, the apparent molar absorptivity was 1. 59×105l·mol - 1·cm- 1 .Beer′s law was obeyed in the range of 0 to 8μg/ 25ml Al (III) . The method has been applied successfully to the determination of trace amount of aluminium in tap and river water samples.