Methylisobutylketone was explored as electrochemical solvent. The purification method of methylisobutylketone, the accessible potential range of this solvent in the presence of 0.1 M tetrabutyl-ammonium perchlorate and the half wave potentials of some typical substances were investigated. Many organic solvents have been explored as electrochemical solvent. Methyl-isobutylketone (MIBK), which has some suitable physical properties as shown in Table l., has not been used for the polarographic determination of an organic phase following solvent extraction mainly because of its low solubility of supporting electrolyte. Lithium perchlorate and n-tetrabutylamrnonium perchlorate, however, was found to be suitable for a supporting electrolyte in this solvent. This paper concerns the purification method of MIBK and the polarographic behavior of some typical substances in MIBK.