Provided are a processing method, device, and system for an overlapped multiplexing system. The method includes: receiving encoded information output by a transmit end, where the encoded information is information obtained by performing error-correcting code encoding and overlapped multiplexing encoding on input information; decoding the encoded information according to an overlapped multiplexing decoding algorithm, to obtain a first decoding result; performing error-correcting processing on the first decoding result according to an error-correcting code decoding algorithm, to obtain a second decoding result; and outputting the second decoding result.