[Objective] The aim of the study was to provide scientific evidence for the rational development and comprehensive utilization of Opuntia dillenii. [Method] The volatile oil was extracted from Opuntia dillenii by steam distillation.The compositions of it were separated and identified by GC-MS.[Result] Thirty-five kinds of compositions were identified among them.The relative percentages of each composition was determined by area normalization. The main constituents of it were as follows:trans-Phytol(36.57%),...