The invention discloses a system and method for improving transmission precision of a digital signal under low bit width AD condition. The system comprises a data processing module, a predistortion module, a DA module, a power amplifier module, an AD module and a data recovery module which are sequentially connected, wherein the system further comprises a parameter calculation module connected tothe predistortion module and the output end of the AD module; the signal input end of the data processing module is used as the signal input end of the system, and the signal output end of the data recovery module is used as the signal output end of the system. The system and method provided by the invention can further improve the transmission precision of the digital signal under the condition that the effective bit width of the AD is limited, and obtain the effect that only the high bit width AD can achieve.