This standard specifies a method for the determination of thiocyanate content in pyrotechnic industrial wastewater, using isonicotinic acid-pyrazolone Spectrophotometric method, spec-trophotometry for analysis. This method is suitable for the detection of wastewater from pyrotechnic production plants, with a measurement range of 0.15 to 1.5 mg/L and a minimum detection concentration of 0.04 mg/L. During the determination process, if the content of mercury cyanide complex exceeds 1 mg/L, it will interfere with the results. This standard is suitable for environmental monitoring and routine testing of wastewater from the pyrotechnic industry to ensure that the concentration of thiocyanate in wastewater is controlled within a safe range.