The invention belongs to the technical field of aeroengine rotor system tests, and relates to a rotor test bench of a spigot connecting structure, and a test method. The test bench is mainly composedof a test sensing system, a rotor-support system and an electrical control box; the test sensing system is mainly composed of vibration test software, a collection card chassis, a collection card, a data collection system, an LMS test device, a modal force hammer and sensor fixing frames; the rotor-support system is mainly composed of a base, a left bearing seat bracket, a left bearing seat, a rotating shaft, a left fixing disc, a left spigot disc, a right spigot disc, a right conical cover, a locking nut, a right bearing seat, a right bearing seat bracket, a variable frequency motor, a motorseat and a deep groove ball bearing; and the electrical control box is connected with the variable frequency motor for adjusting the rotating speed. The rotor test bench provided by the invention is used for studying the influence of the spigot connecting structure and related parameter changes on the inherent characteristics and dynamic characteristics of the rotor system, and providing a test basis for the design of the spigot connecting structures of aeroengines.