The present invention relates to a purification agent for adsorbing volatile chlorides in light hydrocarbon tail gas, and a preparation method thereof. The purification agent comprises a carrier and active components, and is characterized in that the carrier is active carbon or a molecular sieve, the active components comprise a soluble iron salt and potassium permanganate, and a mass ratio of the active carbon or molecular sieve to the soluble iron salt to the potassium permanganate is 85.0-98.0%:1.0-10.0%:1.0-5.0%. According to the present invention, with the purification agent, the harmful volatile chlorides in the light hydrocarbon tail gas can be removed during the industrial production or experiment process through chemical adsorption and physical adsorption at the normal temperature; and the purification agent has characteristics of simple component, easy obtaining and low cost, and the method has characteristics of simple preparation process, easily available raw materials, low production cost, and no environmental pollution.