The volatile oil was extracted from leaf of Cratoxylum formosum(Jack) Dyer subsp. pruniflorum (Kurz) Gogelin in Xishuangbanna of Yunnan Province by steam distillation and its constituents were analyzed by GC-MS technique. The results show that 84 peaks are separated from the volatile oil and 70 compounds are identified, which represents 96.91% of total content. Sesquiterpenoids are the major chemical constituents in the volatile oil, accounted for 86.01% of total content.The major compounds are caryophyllene(23.99%), α-cedrene(10.57%), curcumene(8.75%) and α-caryophyllene(8.57%), etc. The results provide basic data for comprehensive utilization of C. formosum  subsp. pruniflorum.