The invention relates to a purple sweet potato chocolate crisp and preparing method thereof, which belongs to the technical field of food ingredients. The purple sweet potato chocolate crisp, prepared from, by weight: 50-70 parts of sugar, 100-160 parts of palm oil, 20-60 parts of cocoa butter, 10-30 parts of cocoa liquor, 0-10 parts of cocoa butter substitute, 10-40 parts of coconut oil, 20 to 40 parts of purple sweet potato powder, 20-50 parts of cooked flour, 0.05-0.3 parts of monoglyceride fatty acid ester, 0.01-0.2 parts of polyglycerol fatty acid ester, 0.5-2 parts of phospholipid, 0.05-0.2 parts of salt and 0.01-0.3 parts of essence. The purple sweet potato chocolate crisp tastes sweet, nutritious, natural and bright color, withnatural purple sweet potato flavor, making the composition of chocolate crisp nutrition more reasonable, with diversified taste, while simplifying the production process.