NOVELTY - Preparing a catalyst comprises: forming (10) a solution of a solvent, a precious metal precursor, a catalyst substrate, a reducing agent and a stabilizer; homogenizing (12); and reducing (14) the precursor to precious metal nanoparticles and depositing the nanoparticles onto the substrate to form catalyst particles. Reducing and depositing comprise: increasing a temperature of the solution with microwave irradiation at a controlled rate of 8-12 degrees C/minute to a predetermined temperature that is less than 300 degrees C; and holding at predetermined temperature to complete reduction and depositing.    USE - The method is useful for preparing a catalyst (claimed) which is used as fuel cell catalyst.    ADVANTAGE - The method provides: rapid synthesis of ultra-low loading catalyst using controlled microwave heating; and ultra-fine metal catalyst nanoparticles with a low degree of agglomeration and good dispersion on the support, both of which contribute to optimum catalytic activity.    DETAILED DESCRIPTION - Preparing a catalyst comprises: forming (10) a solution comprising a solvent, a precious metal precursor, a catalyst substrate, a reducing agent and a stabilizer; homogenizing (12) the solution; reducing (14) the precious metal precursor to precious metal nanoparticles; and depositing the precious metal nanoparticles onto the catalyst substrate to form catalyst particles. Reducing and depositing comprise: increasing a temperature of the solution with microwave irradiation at a controlled rate of 8-12 degrees C/minute to a predetermined temperature that is less than 300 degrees C; and holding the solution at the predetermined temperature with microwave irradiation until the reduction and depositing are detected to be complete.    DESCRIPTION OF DRAWING(S) - The figure shows a flow diagram of a method of rapidly synthesizing a catalyst.    Preparing the solution (10)    Homogenizing (12)    Reducing metal precursor to nanoparticles and depositing (14)    Cooling the solution (20)    Washing the catalyst particles (22)