The vitamin E analogue, α-tocopherol succinate (α-TOS), has a broad anti-tumor effect. α-TOS can induce cancer cells apoptosis and suppress tumor growth by targeting mitochondria. Low bioavailability of α-TOS is the major problem encountered with formulation development. In our study, α-TOS nanoemulsion (α-TOS-NE) was demonstrated as a new drug delivery system of α-TOS to increase the bioavailability. MTT-based cytotoxicity assay and mitochondrial membrane potential (ΔY) were performed on human breast cancer cell lines MCF-7 and human oral epithelial cancer cell lines KB to evaluate in vitro anticancer efficacy of α-TOS-NE. In comparison with free α-TOS, α-TOS-NE exhibited a stronger cytotoxicity and decreased ΔΨ. Pharmacokinetic profiles of I.V. α-TOS-NE group, I.P. α-TOS-NE group, and I.P. free α-TOS group (7% DMSO/93% PEG) were drawn. First of all, nanoemultion (NE) enables the I.V. injection of α-TOS, make it possible to be an I.V. preparation. Second, compare to the I.P. free α-TOS group, I.P. α-TOS-NE group had a higher bioavailability. Thus, NE improved the strong anti-cancer efficacy of α-TOS while increasing its in vivo bioavailability in rats. In conclusion, our laboratory-made NE was a safe drug delivery system for clinical trials and could be a promising formulation for α-TOS by I.V administration.