The invention relates to a membrane-method coupling lime flue gas brine purification process. The process comprises the following steps: underground brine is pretreated, such that impurities such as suspended solids are removed; a scale inhibitor is added, and the mixture is processed through primary nano-filtration treatment; an obtained clear liquid is processed through secondary nano-filtration treatment; clear liquid obtained by secondary nano-filtration is directly subjected to evaporation salt production; a concentrate obtained in the secondary nano-filtration treatment is returned and is subjected to primary nano-filtration retreatment; a concentrate obtained in primary nano-filtration is refined with a lime flue gas method; obtained refined salt water is subjected to nano-filtration treatment; obtained clear liquid is directly subjected to evaporation salt production; a concentrate is returned to be retreated in the lime flue gas processing procedure; brine sludge is subjected to settlement and washing treatments, and is discharged into an abandoned mine.