The invention relates to an underground brine utilization method. The method includes the following steps: suspended matters, silts and other impurities in brine are removed through brine pretreatment; a primary nanofiltration treatment is carried out after the addition of a scale inhibitor, so as to obtain a clear liquor and a concentrated liquor after the primary nanofiltration; the concentrated liquor enters an energy recovery device and then is subjected to a procedure in which brine is evaporated in the sun for salt making; the clear liquor is subjected to a secondary nanofiltration treatment to obtain a clear liquor and a concentrated liquor after the secondary nanofiltration treatment; the clear liquor is used for dissolving salt; the concentrated liquor returns to the primary nanofiltration process for retreatment. Through the underground brine utilization method provided by the invention, brine can be effectively utilized to dissolve salt for sodium carbonate production and extract other products. In terms of production technique, the invention not only shortens and simplifies the original production technique, but also reduces the tedding area and the tedding time, so as to greatly improve the product yield and the product quality; in terms of production costs, medicine inputs for removing ions which are richly contained in the brine (calcium ions, magnesium ions, sulfate radical ions, and the like) are greatly reduced, so that the production costs are considerably lowered.