OBJECTIVE To explore the changes and significance of the level of reactive oxygen species (ROS) and mitochondria membrane potential (Delta Psi) in HepG2 cells under the stress of cisplatin (CDDP). METHODS HepG2 cells were incubated with CDDP. The changes in the level of ROS were determined by a probe (2,7-dichloro fluorescein-ciactate, DCFH-DA) and the changes of Delta Psi were reflected as changes of intensities of fluorescence seen under a laser scan microscope using a probe (rhodamine-123). All these changes in cells at 0 h, 24 h, 48 h, 72 h, 120 h, 168 h were dynamically observed. RESULTS The level of ROS was much higher after the CDDP treatment than the non-treated, and the increase lasted for 24 h and 48 h. Then it started to decrease at 72 h, gradually returning to normal level at 120 h. Under the selective pressure of CDDP, the fluorescence intensity of rhodamine-123 in HepG2 cells was decreasing at 24 h and 48 h, then gradually started to increase at 72 h. There were no such changes in the cells of the controls. CONCLUSION The changes of ROS and Delta Psi in HepG2 cells under the pressure of CDDP suggest that the cells change themselves adapting to such pressures.