The Kelvin probe force microscope (KPFM) measures the contact potential difference (CPD) between the sample and the probe, allowing the surface potential of the sample to be measured. In order to better measure the small change of the surface potential of the sample, a new conducting probe is needed. The stable chemical properties and high conductivity of the metal Iridium can steadily measure the potential difference between the tip samples. The silicon probe was modified by physical vapor deposition (PVD) and the tip was coated with a thin film of iridium. The probe was characterized by transmission electron microscopy (TEM) and energy spectrometer (EDS) before the experiment, and it was proved that the metal iridium film with nanometer thickness did exist on the tip. Finally, the prepared conductive probe was used to measure the silicon surface CPD in the ULTRA-high vacuum KPFM to obtain the surface step potential diagram of the sample.