Abstract: Lithium, as an important energy metal, is an indispensable resource for the future development of new energy industry. Nanofiltration (NF) technology has promising application prospects in the field of lithium extraction from salt lakes with high mass ratio of Mg²⁺/Li⁺ owing to its selective separation mechanism. However, the commercial NF membrane have some defects when applied to lithium extraction from salt lakes. How to design and construct positively charged composite nanofiltration membranes with high lithium selectivity and high stability is an urgent problem to be solved in promoting NF technology in efficient extraction of lithium resources. This paper summarizes the research progress of positively charged nanofiltration membranes for lithium extraction from salt lakes brine with high mass ratio of Mg²⁺/Li⁺. And it introduces in detail the effects of different construction strategies such as new monomer selection, lithium-ion channel design, introduction of interlayer and reverse interface polymerization on the structure and lithium-magnesium separation performance of composite nanofiltration membranes, and also points out the current problems and future development trends. This review provides a new insight for the construction of positively charged composite NF membrane to extract lithium, and promote the application of NF membrane technology in the extraction of lithium in salt lakes.