Method and system for extracting lithium from salt lake

The invention relates to a salt lake lithium extraction method and system.The salt lake lithium extraction method comprises the steps that raw brine is pretreated; carrying out pre-nanofiltration comprising at least two times of nanofiltration processes on the pretreated raw brine; carrying out primary evaporative crystallization on the produced water subjected to pre-nanofiltration to obtain mother liquor containing lithium ions; carrying out multi-stage nanofiltration comprising at least three times of nanofiltration processes on the mother liquor, and carrying out secondary evaporative crystallization on produced water; performing second-stage dialysis nanofiltration on part of the concentrated water subjected to the multi-stage nanofiltration, and refluxing the produced water to the multi-stage nanofiltration; carrying out first boron removal adsorption on the mother liquor subjected to secondary evaporative crystallization to obtain produced water for forming lithium carbonate precipitate; mixing a part