The HORIBA micro-XRF system performs two applications for proton exchange membrane fuel cell (PEMFC) catalyst research: One is Pt catalyst uniformity imaging within a catalyst sheet thanks to the imaging capability. The other is Pt catalyst loading mass determination on average, which is a popular application of EDXRF. Through the experiments, we successfully visualized aggregates of Pt catalyst in our samples, and we also got a good linearity of calibration curve for Pt catalyst loading mass determination.