Disclosed is a method for highly efficient separation and enriching lithium, comprising: pre-treatment in which brine from a salt field is subjected to dilution at least twice and filtration at least twice to obtain pre-treated brine; separation in which the pre-treated brine is subjected to separation in a nanofiltration separation system to obtain nanofiltration freshwater and nanofiltration concentrated water; first concentration in which the nanofiltration freshwater is subjected to a first concentration in a reverse osmosis system to obtain reverse osmosis concentrated liquid and reverse osmosis freshwater; and second concentration in which the reverse osmosis concentrated liquid is subjected to a second concentration in an electrodialysis system to obtain electrodialysis concentrated water and electrodialysis freshwater, the electrodialysis concentrated water being a solution rich in lithium ions. The method achieves the goal of increasing the efficiency of magnesium-lithium separation and the efficiency of lithium enrichment by means of coupling different membrane separation techniques and subjecting the brine from a salt field to multiple dilutions. The enriched lithium ions reach a lithium-ion concentration required for the preparation of a high-purity lithium salt.