Underground brine from Laizhou Bay in China is one of the most important natural recourses to produce sodium carbonate and other chemical products. Nanofiltration (NF) process was employed to refine this brine via lab-scale experimental investigation and large-scale industrial application. The work reported here indicates that the refined brine generated from the NF system can be directly used in Na₂CO₃ production in Shandong Haihua soda plant. The output of the whole NF system (assembled with about 6300 NF spiral wound membrane elements) was 3.5 × 10⁴–4.1 × 10⁴ m³/d. The total investment of the NF system was about 280 million yuan ($42 million). To produce one cubic meter of refined underground brine (permeates of NF system), the electric energy consumption of the NF system is 3.23 kWh and the responding cost accounts for 26 % of total value, the salary cost is only 0.46 yuan, 5.3 % of total cost. This NF system has been running successfully for more than 3 years, which brought great economic benefit for industrial soda production and provided one feasible way to utilize brine in seawater desalination.