The invention discloses a preparation method of a 4-thio-pyrazolone derivative. According to the method, a pyrazolone derivative is directly applied to react with sulfonyl chloride in the presence of potassium iodide and triphenylphosphine to synthesize the 4-thio-pyrazolone derivative, wherein the used solvent is 1,4-dioxane, the reaction temperature is 60-100 DEG C, and the reaction time is 8-24 hours; and gradient elution is carried out on dichloromethane and methanol as a mobile phase at the volume ratio of (40 to 1) to (20 to 1) to obtain a white or light yellow solid. A series of thio-pyrazolone compounds are synthesized by the novel method for the first time, and can be used as important medical intermediates of analgesic medicines, antipyretic medicines and antibacterial medicines.