Solid liquid extraction of copper ion (I) with 2, 9-dimethyl-l, l0-phenanthroline (neo-cuproine, DMP) into molten naphthalene followed by chloroform spectrophotometric determination has been studied experimentally. The ternary complex Cu(I)-DMP-ClO_4 was extracted quantitatively into molten naphthalene in the range of pH from 5 to 6 at 85℃. Absorbance was spectrophotometrically determined at 459 nm against the reagent blank after the solid naphthalene layer was anhydrously dissolved in chloroform. Beer?(r)s law is obeyed over a concentration range of 0.5- 70 μg/mL. The molar absorptivity and Sandell’s sensitivity are 1.0×10~4 L/(mol.cm) and 0.0099 μg·cm~2 respectively. In addition, the various conditions on determination and the interference of coexisted ions were discussed, and the method was applied to the determination of copper ion both in tea samples and cadmium sulfate reagents. The results are in good agreement with those obtained by ICP AES method. Solid liquid extraction of copper ion (I) with 2, 9-dimethyl-l, l0-phenanthroline (neo-cuproine, DMP) into molten naphthalene followed by chloroform spectrophotometric determination has been studied experimentally. The ternary complex Cu (I) -ClO_4 was extracted quantitatively into molten naphthalene in the range of pH from 5 to 6 at 85 ° C. Absorbance was spectrophotometrically determined at 459 nm against the reagent blank after the solid naphthalene layer was anhydrously dissolved in chloroform. Beer? (R) s law The molar absorptivity and Sandell’s sensitivity are 1.0 × 10 -4 L / (mol.cm) and 0.0099 μg · cm -2 respectively. and the interference of coexisted ions were discussed, and the method was applied to the determination of copper ion both in tea samples and cadmium sulfate reagents. The results are in good agreement with those obtained by ICP AES method.