The invention discloses an HPLC method for determining ten synthetic colorants in a cosmetic simultaneously. According to the method, tetrahydrofuran, dimethyl sulfoxide and methyl alcohol are used for extracting the colorants in a sample under the auxiliary condition of ultrasonic wave, the colorants are separated on a chromatographic column of EclipseXDB-C18 (3.5 mu m, 4.6*150mm) through high-speed centrifugal clarification, acetonitrile and 0.02 mol / L of an ammonium acetate solution with the pH of 4.6 are taken as mobile phases for gradient elution, a diode array detector is used for performing determination, and quantification is performed with an external standard method. The method can simultaneously determine ten synthetic colorants of pigment red 57, pigment orange 5, acid yellow 36, pigment red 53, acid purple 49, rhodamine B, solvent blue 35, Sudan red II, Sudan red IV and disperse yellow 3, and the determination minimum is 20 mg / Kg. The method is simple, fast, sensitive and suitable for quantitative determination of colorants in oily, powdery and paste cosmetics.