This standard applies to the determination of fluoride content in surface water, groundwater and industrial wastewater, using the Ion selective electrode method. The measurement range is wide, the minimum detection limit is 0.05mg/L, and the upper limit of the determination can reach 1900mg/L. This method determines the concentration of free fluoride ions, which does not interfere with common anion and cation, but should pay attention to the interference of high-valent cation and hydrogen ions. The pH value of the solution needs to be controlled between 5 and 8, and sample distillation pretreatment is required if necessary.