The invention relates to the technical field of communication, and discloses a gain sharing device of an interference cancellation system, a method and an interference cancellation system. The device, the method and the system are used for solving the technical problem that in the prior art, different gain sharing data can not be output on the basis of different interference cancellation devices. The device comprises an input control circuit, an accumulation circuit and an output control circuit, wherein the input control circuit is used for obtaining input data from N interference cancellation devices and determining ith reconstruction data of the ith interference cancellation device according to ith input data of the ith interference cancellation device, N is a positive integer, and i is an integer from 1 to N. The accumulation circuit is used for accumulating the reconstruction data, determined by the input control circuit, of the N interference cancellation devices, and obtaining accumulative reconstruction data. The output control circuit is used for aiming at the ith interference cancellation device and determining ith output data corresponding to the ith interference cancellation device according to the accumulative reconstruction data.