The present disclosure provides a vibration exciting system and an apparatus for testing an aero-engine rotor, relating to the field of aero-engines, to improve the universality of the vibration exciting system. The vibration exciting system comprises a mounting ring, fixing parts, holders, guide rails, and nozzle assemblies. The mounting ring is configured to be annular; one ends of the fixing parts are fixedly connected to the mounting ring; the holders are slidably mounted at the other ends of the fixing parts, the plurality of holders being arranged circumferentially of the mounting ring; each guide rail connects two adjacent holders, connection positions of the guide rail and the holders being adjustable; and the nozzle assemblies are mounted on the holders. The radius size of a spraying area enclosed by the nozzle assemblies is adjusted by adjusting the positions of the holders on the fixing parts.