The invention discloses a preparation of PERC battery back pole slurry. The preparation method comprises the steps of: 1) putting tetraethyl orthosilicate, triethyl phosphate, boric acid and organic metal salt in a reaction still in proportion, adding absolute ethyl alcohol as a reaction medium, uniformly stirring the materials, adjusting the PH value of the solution to 3.5-6.5, carrying out reaction and ageing at room temperature, separating the supernatant liquid to obtain glass slurry, and drying and grinding the glass slurry to obtain glass powder; 2) adding a solvent, a thickener and an additive in the reaction still in proportion, and carrying out stirring and fusion to form a uniform organic bond; and 3) adding silver powder, a conductive filling agent, the glass powder and the organic bond in a ball milling tank in proportion; adding a ball milling medium, carrying out grinding and dispersion on a ball mill for 6-7 hours, and separating the ball milling medium to obtain the PERC battery back pole slurry. The synthesized glass powder has favorable ingredient stability and granularity uniformity. According to the preparation method, the ingredient stability of the slurry is improved and the bad influences, on the workshop environment, of organic volatile matters generated in the production process are reduced.