Abstract <p>The separation of Mg²⁺ and Li⁺ ions is a significant technology for recovering lithium from Salt Lake. In this study, we adopted gamma ray irradiation method to prepare the poly(<i>N</i>-isopropyl acrylamide) (PNIPAM) grafted polyvinylidene fluoride (PVDF) (PVDF-g-PNIPAM) ultrafiltration (UF) membrane. The Fourier transform infrared spectroscopy (FTIR) was used to characterize the pristine PVDF membrane and PVDF-g-PNIPAM modified membrane, and the results confirmed that the grafting reaction was successfully achieved via gamma ray irradiation. The scanning electron microscope (SEM) was used to characterize the microsurface and cross-sectional morphology of several membranes. it was found that the pore size of the PVDF-g-PNIPAM modified membrane was effectively reduced, and that many dense pores were scattered in the support layer of PVDF-g-PNIPAM modified membrane. Different membranes were used to separate the fluid containing Mg²⁺ and Li⁺ ions. The findings revealed that the PVDF-g-PNIPAM modified membrane had a good retention effect on Mg²⁺ ions and could retain maximal Li⁺ ion penetration, resulting in excellent separation of Mg²⁺ and Li⁺ ions and setting the groundwork for future study on lithium extraction from salt lakes.</p>