The screw drill tool is a shaft system consisting of a number of rotating shafts connected by a universal coupling， which is used to transfer torque to drive the bit motion. However， owing to the installation or wear and tear of the universal coupling itself， the axial misalignment of the drilling tool will appear， leading to a series of failures， such as offset of the screw motor rotor coupling， bearing movement， shaft deformation， oil film instability， etc.， leading to vibration of the tool and a series of hazards. Therefore， it is of great significance to study the failure mechanism of downhole power drilling tool misalignment， grasp the characteristics of different failures， and timely diagnose the failures under laboratory conditions， so as to reduce or avoid the failures caused by misalignment of the rotor coupling. In this paper， the DHRMT double-span rotor bench is used to simulate various downhole drilling tool failures through setting of rotor misalignment， and the vibration characteristics caused by rotor misalignment is obtained through experiments so as to provide a reference for downhole power drilling tool design and improvement.