Mercury (II) formeda colour complex with rhodamine 6G and potassium iodide in the presence of arabic gum in a medium of 0.4-1.6 N-H3PO4. Beer's law was obeyed for 1-6µg/25m1 of mercury. The apparent molar absorptivity was 1.7·105 1·mol-1. cm-1.The Sandell sensitivity was 1.8·105/µg/cm2.The complex is stable in three hours at 15-25℃.