Objective To investigate the effects and mechanism of 3-methyladenine （3-MA， an autophagy inhib-itor） on the apoptosis of hepatocellular carcinoma cell line SMMC7721 induced by 5-fluorouracil （5-FU）. Methods The autophagy was observed using fluorescent microscope by monodansyicadaverin （MDC） staining. The viability of SMMC-7721 cell induced by 5-FU was measured using CCK8 assay before and after autophagy inhibited by 3-MA， meanwhile the apoptosis of SMMC7721 cell was determined via AnnexinⅤ/PI assay. The light chain 3 protein （LC3， the autophagy specific protein） and caspase-3， PARP protein were detected by Western blot. Results The autophagy of SMMC7721 cell could be induced by 5-FU after treatment for 48 h， the cell survival rate was （60.73±2.65）%， and the apoptosis rate was （40.42±2.34）%. Compared with the group of 5-FU treatment， the survival rate of SMMC7721 cell in the combination of 5-FU and 3-MA after treatment for 48 h decreased to （42.31±1.32）% （P＜0.01）， and the apoptosis rate increased to （60.92±2.99）% （P＜0.01）， meanwhile the expressions of LC3-Ⅱ， activation fragment of caspase-3， and cleavage frag-ment of PARP significantly increased （P＜0.01）. Conclusions Autophagy is a protective phenomenon during the SMMC7721 cell line apoptosis induced by 5-FU， and autophagy inhibition may enhance the sensitivity of SMMC7721 cell line to 5-FU treatment， which is probably associated with the activation of caspase-3 and cleavage of PARP. Therefore， autophagy inhibition could be a promising strategy for adjuvant chemotherapy in hepatocellular carcinoma.