Abstract: Objective: To investigate the mechanism of cellular apoptosis of human glioma U251cell line and the effect of telomerase activity and expression of human telomerase reverse transcripase (hTERT) by elemene. Methods: Human glioma U251 cells were treated with elemene, the inhibitory ef-fect was then examined using MTT and the IC50 was worked out. The morphological alterations was observed by inverted microscope and electron microscope and the apoptosis was evaluated by flow cy-tometry analysis and light microscopy. The telomerase activity was determined by telomeric repeat assay protocol (TRAP) and the expression of bcl-2 and hTERT gene were examined by RT-PCR. Results:Our studies showed that elemene had a markedly antineoplastic activity on glioma U251 cell line with the way of dose- and time-dependence and IC50 was 0.062mg/ml. After administration of elemene the cellular morphology became smaller under inverted microscope and the apoptotic cells and bodies werefound under electron microscope. The flow cytometry analysis showed that elemene inhibited the cellcycle transference from phase S to phase G ₂ /M and induced apoptosis. The apoptosis in glioma cells was observed by light microscope. Elemene decreased telomerase activity, in a time- and dose- dependentmanner. Elemene decreased the expression of bcl- 2 and hTERT gene by RT- PCR examination. Con-clusions: Elemene induced apoptosis of human glioma U251 cell line, inhibited the telomerase activity,the molecular mechanisms of elemene effect on U251 cell may be related to down- regulation of hTERTgene expression and then decrease telomerase activity through the inhibition of bcl- 2 gene.