The invention discloses an initial MCS configuration adjusting method. The initial MCS configuration adjusting method comprises the steps of: in a pre-set period, according to HARQ information of userdevices corresponding to various coverage levels, respectively calculating the demodulation probability information of the various coverage levels; and, adjusting the initial MCS value of a narrow-band IOT system respectively according to a comparison result of the demodulation probability information of the various coverage levels and the set probability threshold. The invention further discloses an initial MCS configuration adjusting device. Due to the HARQ information of all the user devices under the various coverage levels of cells covered by the narrow-band IOT system in the pre-set period, the initial MCS value is adaptively adjusted; the problem of poor overall performance of the system, such as more retransmission of the user devices and low system resource utilization rate, dueto unreasonable initial MCS configuration can be effectively solved; the user device demodulation performance, the system resource utilization rate and the initial MCS configuration scene applicability and accuracy are greatly increased; and the overall performance of the system is greatly improved.