Objective To improve the digestion method of sewage samples for determing mercury with cold atomic absorption spectrometry.Methods 1+1 aqua fortis was used in microwave digestion of sewage samples instead of KMnO4-K2S2O8,then mercury was determined by cold atomic absorption spectrometry.Results The linear range was 0-10.0 ?g/L,the detection limit was 0.25 ?g/L,the relative standard deviation was less than 2.7% and the recovery rate was 95.0%-102.0%.It proved that the results by 1∶1 aqua fortis by microwave had high.Conclusion Compared with the KMnO4-K2S2O8 digestion method,microwave digestion method is simple,sensitive and suitable for determination of heavy metals in the environmental samples.