Abstract: Supported liquid membranes (SLM) were prepared with poly (4 -methylpentene-1)(TPX) as support polymer and tributyl phosphate (TBP), dibutyl phthalate (DBP) and dibutyl sebacate (DBS) as supported liquids. The performance of oxygen enrichment of these membranes has been compared. The permeabilities of the supported liquid membranes were higher in varying degrees than that of pure TPX, while their separation factors were lower. The separation factor α_O/N of SLM containing DBS was higher than that of SLM with TBP and DBP. SEM photographs were recorded to elucidate the difference in the performance of the SLM obtained.