Determination methods of trace Hg(Ⅱ),Cu(Ⅱ) and Cd(Ⅱ) were established based on the combination of LPME of dithizone-chelate for high enrichment,strip shape sampling-TLC and digital image-processing for quantitative analysis.Detection limits of Cu(Ⅱ),Hg(Ⅱ) and Cd(Ⅱ) were 1.5 ng/mL,1.3 ng/mL and 2.5ng/mL,respectively.RSDs were 1.2%,4.0% and 2.7%,respectively.The proposed methods have the advantages of convenience,sensitiveness,precise and economicls.The methods were applied to the determination of these elements in a pool water and mud,with satisfying results.