Abstract: Pyrolytic gas chromatography was used in the study of classification of heroin by the hierarchical clustering of pyrolytic cracking chromatograms. To obtain a correct evaluation on the feasibility of using a platinum coil pyrolyzer in the analysis of heroin solutions,selection of similarity measurement and method of clustering in the hierarchical clustering was firstly performed. And then by using the correlationship analysis and hierarchical clustering,reproducibility of results of the cracking chromatograms were determined. Satisfactory results of evaluation were obtained. Finally,cracking chromatograms of 10 kinds of heroin were submitted for the hierarchical clustering analysis,and results of classification of heroin were obtained.