Embodiments of the present disclosure provide an uplink information demodulation method, an apparatus, and an uplink information demodulation system. and relate to the field of communications technologies. After an MCS index is selected for a terminal device, reduction processing is performed on the MCS index according to a preset MCS index reduction exponent, a reduced MCS index is indicated to the terminal device, frequency offset estimation is performed on the terminal device by using a recorded historical frequency offset value, and a PUSCH sent by the terminal device according to the reduced MCS index is demodulated after the frequency offset estimation. A frequency offset value is determined by using the prerecorded historical frequency offset value, so that the frequency offset value does not need to be determined in an existing manner of adding a DM-RS symbol to a 0.5-millisecond TTI.