Abstract: A method of determining a first distance between a probe and a wafer held by a wafer probe station includes adjusting a microscope at a specific magnification; moving the microscope perpendicularly relative to a chuck to focus on the chuck to obtain a clear image of the chuck; defining a specific position of the microscope after the clear image of the chuck is obtained; maintaining the specific magnification of the microscope and moving the microscope perpendicularly relative to the chuck from the specific position by a travelling distance to focus on the probe to obtain a clear image of the probe; and determining the travelling distance minus a thickness of a wafer to be placed on a side of the chuck facing to the microscope as the first distance between the probe and the wafer.