The invention belongs to the field of application of bioengineering technology, and particularly relates to a preparation method of tremella aurantialba fermentation liquid polysaccharide with anti-oxidation activity. The polysaccharide is white or light-yellow powder which is prepared from a slant strain of tremella aurantialba by the steps of activation, shake flask liquid fermentation, ethanol precipitation, deproteinization, chromatography and dialysis of a sephadex column G-100 and freeze drying. The output is 6.6mg/100mL fermentation liquid, the polysaccharide content is 85.85% according to measurement by a phenol-sulfuric acid process, and the polysaccharide can be used for preparing a healthcare product with anti-oxidation and anti-aging functions.