NOVELTY - Preparing core cell catalyst comprises preparing a core by adding a complexing agent into polyalcohol reductant solution or mixed solution of the polyalcohol reductant solution with water, performing ultrasonic treatment and agitating for dissolving the complexing agent completely, and then adding metal chloride or metal nitrate, performing the ultrasonic treatment, agitating and mixing uniformly and then adding the oxidized carbon carrier, agitating and performing the ultrasonic treatment to disperse uniformly and adjusting the pH to 8-10 by alkaline solution.    USE - The method is useful for preparing core-shell catalyst, which is useful for low-temperature fuel battery.    ADVANTAGE - The method is capable of preparing core-shell catalyst in a simple manner.    DETAILED DESCRIPTION - Preparing core cell catalyst comprises preparing a core by adding a complexing agent into polyalcohol reductant solution or mixed solution of the polyalcohol reductant solution with water, performing ultrasonic treatment and agitating for dissolving the complexing agent completely, and then adding metal chloride or metal nitrate, performing the ultrasonic treatment, agitating and mixing uniformly and then adding the oxidized carbon carrier, agitating and performing the ultrasonic treatment to disperse uniformly, adjusting the pH to 8-10 by alkaline solution with the mass concentration of 5-10% and then placing the solution into an autoclave to react for 4-12 hours at 100-160 degrees C, after finishing the reaction, cooling the autoclave to room temperature and then using diluted aqueous nitric acid solution with the mass concentration of 5-10% to adjust the pH of the reaction solution in the autoclave to 4-6, washing by secondary water and filtering the reaction solution till there is no chloride ions in filtrate, drying obtained filter cake in vacuum at 60-80 degrees C to achieve constant weight to obtain a catalyst precursor, where the mass of the carbon carrier is equal to 4-8 times of the theoretical mass of the total metal of the reduced metal chloride or metal nitrate, the molar ratio of the polyalcohol reductant to the total metal ions in the metal chloride or metal nitrate is 1:1-1:10, the molar ratio of the complexing agent to the total metal ions in the metal chloride or metal nitrate is 2:1-2.5:1, the molar ratio of the metal chloride or metal nitrate to the polyalcohol reductant is 1:0.3-1:3, the complexing agent is sodium citrate, citric acid or disodium ethylenediamine tetraacetate, and the polyalcohol reductant is ethylene glycol, isopropyl alcohol, glycerin or n-butyl alcohol, stabilizing the catalyst precursor for 1-3 hours at 100-150 degrees C in inert atmosphere and preparing a shell using the catalyst precursor processed as the core, preparing the shell on the core by an impregnation-reduction method, a high-pressure organic colloidal method, a microwave method or an electrode position method, and then loading the core together with the shell on the carbon carrier to obtain the core-shell catalyst, where the core-shell catalyst uses platinum as a shell and metal comprising ruthenium, palladium, ferric, cobalt, nickel, copper, tin, iridium, gold and silver as a core.