This standard specifies the determination method of chlorine content in mg and magnesium alloys, which is applicable to the original mg ingot, mg powder and aluminum magnesium alloy powder. The determination range is 0.0010% to 0.0500%. The method includes dissolving the sample with sulfuric acid, reacting chlorine with silver nitrate (AgNO3) in the presence of acetone to form a silver chloride emulsion, and measuring its Absorbance at 420 nm wavelength by spectrophotometer. Reagents include mg, nitric acid, acetone, sulfuric acid, silver nitrate (AgNO3) solution and chlorine standard solution. The standard solution of chlorine is used for calibrating and determination to ensure the accuracy of test results. This method can effectively determine the trace chlorine content in mg and magnesium alloy.