Cadmium is one of the heavy metals which have high toxicity and can be accumulated in bodies. Its content in environment is very low. In the determination of Cd, high sensitivity is required. A new detection method formed by two kinds of dye has been studied. Three components system of Cd-Phen-Bromophenol Blue(BPB) is first extracted by CHCl₃. Then the solution of Na₂CO₃ is added to destroy the three components system. Then Butylrhodamine B (BRB) is added to form dye ion pair with BPB. BPB-BRB ion pair is extracted by toluene. The absorbance is measured at 589 nm. The apparent molar absorptivity is 4. 08×10⁵ L/(mol·cm). Beers law is obeyed over the concentration range of 6. 0×10^-8 ～3. 1×10^-5 mol/L. The recovery rate is in the range of 98.0%～101.8%. RSD is 3.2%. The proposed method is applied to the determination of trace Cd in wastewater samples, and satisfactory results have been obtained.