The invention discloses a drilling mud formula and an automatic mud circulation purification device, and relates to the technical field of drilling mud. The mud specifically comprises mud raw materials, and the mud raw materials comprise, by weight, 1000 parts of clear water, 20 parts of bentonite, 4 parts of polyacrylamide, 4 parts of vegetable gelatin, 6 parts of potassium humate, 3 parts of sodium carboxymethyl cellulose, 3 parts of ferrochrome sodium lignin sulfonate, 4 parts of sodium carbonate, 4 parts of barite fine powder, 3 parts of dry sawdust, 4 parts of asbestos and 5 parts of polyacrylamide flocculant. The high-quality bentonite is selected, so that the slurry has the advantages of low relative density, low viscosity, small sand amount, small water loss, thin mud cake, strong stability, strong wall fixing capability, small rotation resistance of a drilling tool, high drilling rate, high slurry making capability and the like; the viscosity of the slurry can be increased by using sodium carboxymethyl cellulose, so that a thin film is formed on the surface of the soil layer to prevent the hole wall from peeling off, and the effect of reducing the water loss is achieved.