The invention discloses a method for preparing a standard carmine sample colorant for analyzing food and relates to a synthesis method of the colorant for analyzing the food. The method comprises the following steps that firstly, a mixed solvent composed of aqueous sodium chloride solution and % ethyl alcohol is re-crystallized in four times, a prepared filter cake enters an NF separating membrane device for removal of sodium chloride after being dissolved in water, and the prepared filter cake is concentrated until the conductivity does not decline basically; and the concentrated liquid is dried, crushed and sieved to prepare a standard sample. The carmine colorant is re-crystallized in four times by the mixed solvent composed of 13% aqueous sodium chloride solution and 95% ethyl alcohol. The concentrated liquid is dried and crushed at 90 DEG C and screened by a 60-mesh sieve to prepare the standard sample. The standard value of the national standard synthetic colorant sample is improved in accuracy by scientifically verifying uniformity and steadiness of the synthetic colorant and strictly controlling the impurity content of the raw material, and the uncertainty can be relatively scientifically, reasonably and comprehensively evaluated.