To investigate the mechanism on Capparis spionosa L polysaccharide(CSPS) inducing apoptosis in HepG2 human hepatoma cell. MTT was ddopted to determine if CSPS had cytotoxic effect on HepG2. Morphology of HepG2 changed with dosages of CSPS was detected by laser confocal scanning microscope. Flow cytometry(FCM) was used to detect the apoptosis by PI labeling method. Calcium, mitochondrial membrane potential, Bcl-2/Bax of HepG2 cells were detected by laser confocal scanning microscope. The result of MTT showed that CSPS could inhibit the growth of HepG2 significantly. HepG2 cells were shrinkage, fragmentation, appearance of apoptotic bodies by laser confocal scanning microscope. HepG2 cell apoptosis rate was increased gradually with dosage by FCM. Calcium concentration, mitochondrial membrane potential, Bcl-2 protein of HepG2 were decreased, Bax protein content of HepG2 was increased by laser confocal scanning microscope. CSPS induced HepG2 apoptosis by controlling Bax/Bcl-2 in Ca2+ path.