Objective To study the chemical constituents of three kinds of clematis and provide the basis for their further exploitation and utilization. Methods Chemical components were identified by GC-MS. Results The 115 volatile compounds were isolated from the petroleum ether extracts of these plants and identified by GC-MS. The main composition of Clematis chrysocoma var. glabrescens was eicosane（8.45%）， octacosane（7.16%）， squalene（6.81%）， heptacosane（5.78%）， tricosane（3.3%）， lignocerane（2.38%）and BHT（1.11%）； The main composition of Clematis ranunculoide Franch was octacosane（30.37%）， eicosane（18.45%）， squalene（3.06%）， heptacosane（1.6%） and BHT（0.39%）； The main composition of Clematis connata DC was eicosane（5.51%）， palmitic acid（3.82%）， linoleic acid（3.44%）， 9， 12-methyl linoleate（2.47%）， ethyl linoleate（1.56%）， methyl linolenate（1.32%）， 2-Lauryl ether ethanol（1.32%）and（Z）-9-Ene amide 18（1.01%）. Conclusion Systematic analysis was firstly conducted on the compositions and their relative contents of essential oils in three kinds of clematis， which would build foundation for further utilization of this species. Squalene is a variety of biological activity of long chain polyene compounds， thin Clematis chrysocoma var. glabrescens can be used as a new resource of plant squalene.