NOVELTY - A platinum-loaded mesophase carbon microsphere fuel cell catalyst (I) is prepared by (1) performing activation pretreatment on mesophase carbon microsphere via acid modification treatment and/or alkali modification treatment to obtain activation pretreated mesophase carbon microsphere as carrier; and (2) loading the platinum on the activation pretreated mesophase carbon microsphere via chemical reduction deposition or electrochemical deposition using platinum salt solution (S1) to obtain the catalyst (I).    USE - Method for preparing Pt-loaded mesophase carbon microsphere fuel cell catalyst (I).    ADVANTAGE - The method is simple and environment-friendly, and can provide Pt-loaded mesophase carbon microsphere fuel cell catalyst (I) with excellent catalytic performance, low cost, excellent stability, and good corrosion resistance and durability. Through acid modification treatment and/or alkali modification treatment on the mesophase carbon microsphere, few polar functional groups are introduced on the surface of the catalyst carrier, the surface area is significantly enlarged, and the absorption ability is improved, thus the catalyst adsorption capacity is significantly increased, the load and dispersion degree of the Pt in the catalyst carrier can be controlled effectively, the catalytic performance of the Pt is improved, the utilization rate of the noble metal catalyst is enhanced, and the problems associated with existing fuel cell catalyst carrier such as high cost and weak stability and durability can be solved effectively.    DETAILED DESCRIPTION - A platinum (Pt) loaded-mesophase carbon microsphere fuel cell catalyst (I) is prepared by (1) performing activation pretreatment on mesophase carbon microsphere via acid modification treatment and/or alkali modification treatment to obtain activation pretreated mesophase carbon microsphere as carrier; and (2) loading the platinum on the activation pretreated mesophase carbon microsphere via chemical reduction deposition or electrochemical deposition using platinum salt solution (S1) to obtain the catalyst (I). Step (1) is performed by subjecting the mesophase carbon microsphere into acid modification treatment and/or alkali modification treatment, washing with water until it becomes neutral, drying, and cooling to obtain the activation pretreated mesophase carbon microsphere. Step (2) can be performed by mixing the activation pretreated mesophase carbon microsphere with water to obtain carbon paste, slowly adding with platinum salt solution (S1) and then mixing completely, adding with reducing agent solution (S2), regulating the pH to nearly neutral, heating to 40-90 degrees C and insulating for 20-60 minutes, cooling to room temperature, continuously mixing for 12-24 hours, filtering, washing, and drying to obtain the catalyst (I). An INDEPENDENT CLAIM is included for the prepared Pt-loaded mesophase carbon microsphere fuel cell catalyst (I).