In order to make all the measured cadmium of soil sample into test solution, a method by adding hydrochloric acid, nitric acid, hydrogen fluoride and perchloric acid is used to completely digest soil mineral lattice. And the accuracy of determining the heavy metal cadmium in soils by flame atomic absorption spectrometry (FAAS) and Graphite furnace atomic absorption spectrometry (GFAAS) are analyzed through the experiments of sample detection, recovery of standard addition and quality control. The results show that: the former’s relative standard deviation(RSD) is within 3%, the rate of recovery is between 89% ~ 95%, the indoor relative standard deviation of soil sample GSS-5 is 4.8% whose relative error is within ±5%. The latter’s RSD is relatively higher which is between 5% ~10%, the rate of recovery is between 80% ~ 90%; the indoor standard deviation of soil sample GSS-5 reaches to 8.5% whose relative error is -6.21%. Compared with GFAAS, FAAS is more precise and stable, but its detection limit is higher.