The invention relates to an anionic collector for normal temperature flotation of hematite and a preparation method thereof. The anionic collector is prepared from the following raw materials in parts by weight: 12.5-70.0 parts of gutter oil fatty acid, 12.5-70.0 parts of naphthenic acid, 2.0-20.0 parts of N-dilauroyl ethylenediamine sodium triacetate, 1.0-20.0 parts of coconut oil disodium polyoxyethylene sulfosuccinate and sodium hydroxide in an amount which is 0.2 times the total parts by weight of the gutter oil fatty acid and the naphthenic acid. The preparation method of the anionic collector comprises the following steps: stirring the gutter oil fatty acid, the naphthenic acid and the sodium hydroxide for 40-45 minutes at 85-95 DEG C to perform saponification; saponifying for 5-10 minutes after cooling to 30-40 DEG C, adding the N-dilauroyl ethylenediamine sodium triacetate and the coconut oil disodium polyoxyethylene sulfosuccinate, stirring for 5-10 minutes and curing to obtain the anionic collector. According to the method, ore concentration is performed at the normal temperature of 20-25 DEG C, so that the energy consumption is reduced, the energy is saved, the environment is protected, the cost is low, the collection capacity is high, the selectivity is good, the operation concentrate grade is kept, the operation recovery rate is improved, the cost of a flotation reagent is reduced, the waste cooking oil fatty acid is used as a raw material, and a new approach is developed for recycling of gutter oil.