The effects of various experimental conditions on the determination of mercury by cold vapour atomic absorption spectrometry were investigated. Under the optimum conditions, the detection limit of mercury was 0.5 ng.mL-1, and the sensitivity was 1.1 ng.mL-1. The calibration curve was linear in the range of 0-40 ng.mL-1. The analytical procedure of mercury by pressure dissociation method was established by using HNO3, H2SO4 and H2O2(4 + 1 + 1) as oxidant, SnCl2 as reductant in acid medium. The analysis method was successfully applied to the determination of mercry in certified reference material of hair and traditional Chinese medicines, the relative standard deviations were 3.2%, 1.5% and 0.24% respectively. The recovery of mercury was 94.6%-102%. The results obtained were satisfactory. Air can been used as carrier gas instead of high purity argon.