A probe assembly, adapted to test high-speed signal transmission lines of printed circuit boards, includes two pogo pins for providing high-frequency differential test signals, and both sides of the pogo pin include no metal layer (grounding layer). Experiments have found that when the two pogo pins test a to-be-tested object, the test signal will be coupled to the metal layers on both sides of the pogo pins to generate a radiation resonance, resulting in a loss of the test signal on a specific frequency band, and further reducing the effective bandwidth of the probe assembly. The metal layers on both sides of the pogo pins of the probe assembly are reduced, so that the foregoing radiation resonance phenomenon can be avoided.