NOVELTY - The process for preparing catalyst solution for a membrane-electrode assembly in a fuel cell, comprises mixing a catalyst solution (A) and an ion conductive resin solution (B) to form a dispersion, mixing the dispersion with functional additive dissolved in high boiling point solvent or a mixture (C) of low boiling point solvent and water to prepare catalyst ink dispersion, and aging the catalyst ink dispersion. Catalyst particles (3-10 wt.%) are dispersed in water in the catalyst solution. Ion conductive resin particles (10-150 wt.%) are dissolved in water.    USE - The process is useful for preparing a catalyst solution for a membrane-electrode assembly in a fuel cell.    ADVANTAGE - The process ensures an industrial preparation of a catalyst solution for a membrane-electrode assembly in a fuel cell with improved yield, provides excellent electrochemical performance to the fuel cell, and easily controls the amount of catalyst particles to be coated.    DETAILED DESCRIPTION - The process for preparing catalyst solution for a membrane-electrode assembly in a fuel cell, comprises mixing a catalyst solution (A) and an ion conductive resin solution (B) to form a dispersion, mixing the dispersion with functional additive dissolved in high boiling point solvent or a mixture (C) of low boiling point solvent and water to prepare catalyst ink dispersion, and aging the catalyst ink dispersion. Catalyst particles (3-10 wt.%) are dispersed in water in the catalyst solution. Ion conductive resin particles (10-150 wt.%) are dissolved in water and/or low boiling point organic solvent in the ion conductive resin solution. The catalyst solution has a viscosity of 100-300 cps. The secondary particles have a mediate size (d50) of 0.1-2 mu m. The functional additive comprises water-repellent polymers, conductive nanoparticles, pH modifier and leveling agents. An INDEPENDENT CLAIM is included for a process for preparing a membrane-electrode assembly in a fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows a flow diagram for preparing catalyst solution for a fuel cell.