The invention discloses alum-free vermicelli which is prepared from the following raw materials in parts by weight: 0.3-0.5 part of compound gluten fortifier, 0.3-0.5 part of compound phosphate, 2.5-5.0 parts of denaturized starch, 100 parts of starch and a proper amount of water through the steps of mixing, stewing, freezing and airing. The invention also discloses a preparation method of the alum-free vermicelli which is prepared from the raw materials in the weight ratio through the following steps of pulping, filtering, purifying, dewatering, pouring starchy sauce over the dish, curing, vacuumizing, forming, ageing, airing and the like. The vermicelli provided by the invention contains no sulfur dioxide, lead or total arsenic, the aflatoxin content accords with the national standard, the lead content is far lower than the national standard requirement not higher than 100mg / kg; fine sand and dust mixed in the starch can be sufficiently removed through the filtering and purifying processes, and the vermicelli is pure in color and luster and contains the dust content which is not higher than 0.7%; and due to the adoption of the periodical ageing process, the inside and the outside of the vermicelli are frozen uniformly, no barring and white tip phenomena are caused, the broken bar rate is not higher than 3% after rehydration, vermicelli is straight in bar shape, smooth in taste and free of foreign smell.