When　a　quaternary　ammonium　surfactant　has　a　suitable　solubility　in　a　polar　solvent,　it　can　induce　the　phase　self-separation　of　mutually　soluble　polar　and　apolar　mixed　solvents　and　a　stable　interface　between　the　two　phases　can　be　formed.　This　phenomenon　was　attributed　to　the　quaternary　ammonium　surfactant　reaching　suitable　solubility　in　the　polar　solvent　and　driving　out　a　considerable　part　of　the　apolar　solvent,　in　which　the　surfactant　is　insoluble.　As　a　result,　phase　separation　appears.　Using　aqueous　surfactant　two-phase　as　reference,　we　suggest　that　it　be　termed　as　nonaqueous　surfactant　two-phase　(NSTP)　and　also　as　two　oil　phases　for　short.