The invention provides an acid-base-free regeneration method of waste machine oil. The acid-base-free regeneration method comprises the following steps: (1) carrying out rough filtration on the waste machine oil, to be specific, filtering the waste machine oil by using a mesh screen with the meshes of 400-800 to remove relatively large particle impurities in the oil; (2) flocculating, to be specific, adding cationic-type polyacrylamide and aluminium polychloride to the waste machine oil, stirring at the constant temperature of 60-100 DEG C and the stirring speed of 100-220r/min for 3-8 hours, standing still and settling for 3-6 hours, and thus completing flocculation of tiny impurities in the waste machine oil, wherein the weight of the cationic-type polyacrylamide accounts for 5%-20% of the weight of the oil, and the weight of aluminium polychloride accounts for 4%-15% of the weight of the oil; (3) decolorizing, to be specific, adding pulverized fuel ash with the specific surface area of 300-500m<2>/kg to the flocculated oil, stirring for 30-90 minutes respectively at the constant temperatures of 70-90 DEG C, 90-110 DEG C and 110-130 DEG C, and finally settling the stirred oil at the constant temperature for 3-6 hours, wherein the weight of the pulverized fuel ash accounts for 5%-15% of the weight of the oil; (4) separating out impurities, to be specific, filtering and separating the decolorized oil by using an industrial filter press, and thus obtaining regenerated product oil. The acid-base-free regeneration method of the waste machine oil is simple to operate and low in regeneration cost; the regeneration oil is good in quality, relatively high in yield and worthy of popularization.