Abstract: Embodiments of the present application provide a measuring system and method for rotation parameters of a top drive main shaft, and belong to the technical field of oil and gas drilling equipment. The measuring system includes: a first constant velocity helical disk fixedly disposed on the top drive main shaft and rotating about a shaft axis of the top drive main shaft; a first ranging device, configured to contactlessly acquire a first distance between the first ranging device and a side wall of the first constant velocity helical disk; and a data processing unit, configured to determine a rotational angle of the top drive main shaft according to the first distance and a minimum radius and a maximum radius of the first constant velocity helical disk. With the measuring system of the present application, a measurement value of the rotational angle of the top drive main shaft can still be maintained after the system is powered on again.