Green tea seed oil (Camellia sinensis L. Kuntze) samples were used in this work. The tea seed oil contains more than 84% unsaturated fatty acid, such as oleic acid, linoleic acid, and linolenic acid. The most current research on oil extraction is focused on producing biodiesel from vegetable oils. The biodiesel from tea seed oil in itself is not significantly different from biodiesel produced from vegetable oils. Tea seed oils as well, as different vegetable oils, have lower pour point and lower viscosity. Supercritical fluid extraction of tea seed oil was performed to study the effects of various parameters such as pressure, temperature, extraction time, and solvent (methanol) on the yield and composition of the oil. Under supercritical conditions, partial thermal degradation occurs on the double bonds of unsaturated aliphatic carbon chains in fatty acids. Oxidation of methyl esters resulted in the formation of hydroperoxides. Unsaturated fatty acid, such as oleic acid, linoleic acid, linolenic acid, and gadoleic, reach as high as 85.6%. The content of linoleic and linolenic acids in the tea seed oil is 20.5%, while these acids account for 15.9% of the total fatty acids in the supercritical methanol extracts. Partial thermal degradation of the linoleic and linolenic acids may occur in the supercritical methanol extraction due to high temperature (<513 K). The high temperature had a much greater effect on the polyunsaturated fatty acids than saturated and mono saturated fatty acids.