Belonging to the technical field of building base materials, the invention discloses an indoor wall base bottom layer leveling mud with purification function and a preparation and construction method thereof. Leveling putty comprises the following raw materials by weight: 20-50 parts of gypsum, 5-20 parts of 200-400mesh calcium oxide, 20-50 parts of 100-200mesh quartz sand, 10-30 parts of 200-400mesh heavy calcium carbonate, 10-30 parts of 80-200mesh diatomite, 5-10 parts of 80-200mesh volcanic ash, 5-20 parts of 100-200mesh non-calcined diatomite, 1-10 parts of 100-200mesh attapulgite, 1-10 parts of 200-800mesh magnesium aluminosilicate, 0.5-10 parts of 10-30nm nano-zinc oxide, and 0.5-10 parts of 10-30nm nano-titanium dioxide, etc. The leveling mud provided by the invention has the environmental protection functions of regulating humidity and preserving heat, purifying air, decomposing formaldehyde and the like.