The invention belongs to the field of engine rotor performance testing, and particularly relates to a measuring system and method of a torsion angle of rotor blades in an operating state of an engine.The measuring system comprises two or more first sensors, a signal processing and collecting module, a rotating speed sensor and a torsion angle processing module; the two or more first sensors are arranged on the inner ring face of a casing and arranged at the front edge and the tailing edge of the axial position of the same to-be-measured rotor blade; the signal processing and collecting moduleis used for receiving sensor data and converting the data into the blade tip arrival time data of the front edge and the tailing edge of the to-be-measured rotor blade; the rotating speed sensor is used for detecting the rotating speed of the to-be-measured rotor blade; and the torsion angle processing module is used for calculating the torsion angle of the rotor blades. According to the measuring system and method of the torsion angle of the rotor blades in the operating state of the engine, on the basis of first-order torsion and measurement thereof, the feasible measuring method, a feasible measuring model and a feasible measuring formula are provided, the measuring points are arranged easily, calculated related parameters are easy to obtain, the measuring system and method are easy toimplement on the engine, and guiding significance is achieved in torsion angle measuring.