The invention discloses a printing and dyeing auxiliary and a preparation method thereof and relates to the technical field of textile printing and dyeing. The printing and dyeing auxiliary comprises the following raw materials in parts by weight: 8-10 parts of guar gum, 15-17 parts of sodium dioctylsulfosuccinate, 4-6 parts of sodium sulfite, 4-10 parts of polyethylene glycol laurate, 5-7 parts of polyalkyl acrylate, 5-8 parts of sodium carboxymethyl cellulose, 9-11 parts of octadecyl dimethyl benzyl ammonium chloride and 6-9 parts of barium chloride. The printing and dyeing auxiliary disclosed by the invention has good efficacies of improving color fastness, protecting color and preventing color fading, simultaneously can reduce the consumption of dyes, is green, environment-friendly and nontoxic and reduces the cost, thereby having wide industrialization prospect and market value.