Comprehensive utilization method for brine

The invention discloses a comprehensive utilization method for brine. The method comprises the following steps: (1) pretreating underground brine by virtue of an ultrafiltration membrane; (2) performing treatment to obtain refined brine with salt content of smaller than or equal to 8 weight percent and relatively lower divalent ion content and concentrated brine with relatively higher divalent ion content by adopting a nanofiltration membrane; (3) concentrating the refined brine to obtain refined concentrated brine with salt content of greater than or equal to 16 weight percent as well as fresh water with salt content of smaller than or equal to 1 weight percent by adopting a homogeneous membrane electrodialyzer; (4) processing the obtained fresh water into softened water by virtue of an ultrapure water system, and causing concentrated water produced by reverse osmosis to return to step (3) for repeated concentration; (5) tedding and concentrating the obtained concentrated brine to obtain sodium sulfate and s