A new preparation method for the catalyst layer in the electrodes of a polymer electrolyte fuel cell, based on the process of preparing perfluorosulfonate-ionomer (PFSI) colloid, was developed. In this method, both a good network of PFSI and uniformity of PFSIs on Pt particles were achieved with colloid formation of PFSI chains in the specific organic solvents. The applicable organic solvents had dielectric constants ranging from 3 to 10. The PFSI colloids were selectively adsorbed onto the carbon agglomerates with highly dispersed Pt particles on the surface, and a catalyst paste-formation followed. Then the catalyst paste was spread over a carbon paper representing the gas diffusion layer, and two sheets of carbon paper with catalyst paste on them were hot pressed onto an ion-exchange membrane from both sides. This simple preparation method provided high performance in fuel cells at low temperature (50 degrees C).