Atomic fluorescence spectroscopy was used to determine cadmium in seawater. The effects of acidity, KBH4 concentration, carrier gas flow rate, lamp current, and atomizer height on the determination were studied. The measurement conditions were optimized, and seawater samples and accuracy were measured. This method has the advantages of simple operation, low substrate interference, and high sensitivity. The results are reliable and suitable for the determination of cadmium in seawater.