Abstract: The Optimal conditions of the Cd(Ⅰ)-Cadion 2B-Twecn 40 system have been studied.In the NaOHalkaline medium,,a red Cd(Ⅱ)-Cadion 2B-Tween 40 complex forms with ε_510nm=9.80×10⁴.The Ka of Cadion 2Band Surface tension in the system were estimated.It was proved that K_a was increased and the reagent species with absorption maximum at 605nm formed.Using the dual-wave length method at 510-605nm the apparent molar absorptivity for cadmium measured is 2.60×10⁵.The molar ratio of cadmium with Cadion 2B is estimated 1: 3 as by the molar ratio method and continueous variation method.The Beer's law is obeyed in 0-16μg Cd/25ml.Using the proposed method with TEA,IDA,CITmasking mixture,the Cd content in rice samples was determined with satisfactory results.