Bio assay of mercury and cadmium ions were searched using voltammetric analysis using DNA doped carbon nanotube paste electrodes (DCP). The square-wave stripping voltammetryic optimized results indicated working ranges of 1-10.0 ngL-1 and 20-100 ugL-1, Hg(II) Cd(II) within an accumulation time of 120 seconds, in 0.1-M phosphate buffer solutions of pH 6.3. The relative standard deviations of 5 ngL-1 Hg(II) and Cd(II) that observed were 0.14 and 0.22% (n=12), respectively, using optimum conditions. The low detection limit (S/N) was pegged at 0.1 ngL-1 (4.9×10-11M) Hg(II) and 0.2 ngL-1 (1.77×10-10M) Cd(II). The developed methods can be applied to assays in biological fish kidneys and water samples.