Abstract: Objective 　To study the changes of ubiquitin during vincristine (VCR) mediated autophagic apoptosis of Hep G2 cells, and determine the influences of inhibiting ubiquitin-proteasome pathway on this apoptosis and bcl-2. Methods 　To induce autophagic apoptosis of Hep G2 cells t reated with VCR. The apoptosis and the expression of ubiquitin were detected with flowcytometry( FCM) and the expression of bcl-2 was examined by RT-PCR technique. Results 　VCR could significantly increase ubiquitin level in Hep G2 cells that underwent autophagic apoptosis ( P < 0. 01) . There are higher apoptosis rate ( P < 0. 01) and lower expression of bcl-2 in the cells by using VCR combined with lactacystin (a proteasome inhibitor) than that in the cells treated with VCR alone. Conclusion Ubiquitin-proteasome pathway is involved in the VCR-induced autophagic apoptosis of hep G2 cells and in regulating the levels of bcl-2, which might have a role in mediating autophagic apoptosis in Hep G2 cells. The inhibition of Ubiquitin-proteasome pathway can enhance VCR-induced apoptosis in Hep G2 cells.