Total mercury (Hg) concentration provides insufficient information to understand Hg behavior in Hg-contaminated soil systems and to seek potential remediation technologies, because the distribution, mobility, bioavailability, and toxicity of Hg are dependent on Hg forms present in soils. The phase association of Hg in soil is investigated to evaluate potential environmental risk through combination of total Hg determination, soil fractionation, and speciation analysis of Hg in a Hg-contaminated DOE site. Besides total Hg concentration analysis, sequential extraction procedures and thermal desorption techniques were employed to study Hg binding forms in soils in this study. Total mercury concentrations ranging from less than 100 ng/g to more than 30,000 ng/g were detected. The highest form of mercury present in the soil is organically-bound mercury, followed by elemental mercury, and mercury sulfide. Bioavailable and mobile mercury is minimal.