The invention discloses a preparation method for purely-natural yeast powder. The preparation method for purely-natural yeast powder comprises the following steps of: preparing yeast solution, specifically, soaking fruits, grains or plant flowers in honey, malt extract and purified water, standing, and then extracting the yeast solution of fruits, grains or plant flowers, which contains a saccharomyces cerevisiae group and a lactobacillus group; preparing yeast paste, specifically, kneading naked barley powder, malt extract and purified water into the yeast paste, and culturing in four phases; culturing saccharomycetes, specifically, synthesising the yeast solution and the yeast paste into a wet cenobium, and culturing; performing enlargement culture on saccharomycetes, specifically, mixing the wet cenobium with an enlargement culture medium in a certain ratio, and performing enlargement culture on saccharomycetes by proliferating by 100-10000 times, so as to prepare mixed yeast solution; and blending the yeast powder, specifically, mixing the dry substances of glucose, alpha-dry rice meal, vitamin C, corn starch, cane sugar and the like in the mixed yeast solution, and finally preparing the natural yeast powder. The yeast powder disclosed by the invention is completely prepared from natural substances and free from preservative, and has the advantages of being anti-ageing, anti-mildew and long in storage life.