A rectangular probe includes two broad side surfaces and two narrow side surfaces each parallel to a longitudinal direction of the rectangular probe. The rectangular probe includes a middle segment, a first connecting segment and a second connecting segment respectively extending from two opposite ends of the middle segment, a first contacting segment and a second contacting segment respectively extending from the first and second connecting segments, and a stroke structure arranged on the middle segment, the first contacting segment, or the second contacting segment. A longitudinal thru-hole of the stroke structure is formed by penetrating through the two broad side surfaces. Two transverse grooves of the stroke structure are respectively recessed in the two broad side surfaces. The two transverse grooves are configured to move in two directions away from each other so as to reduce a length of the rectangular probe.