A new characterization method, namely membrane voltage measurement method, is proposed. Because the recovery time of membrane potential is dependent on the size of optoporation, establishing the relationship between the size of cytomembrane optoporation and the laser energy threshold can provide theoretical support for importing different exogenous substances into cells. In this study, gastric cancer cells are cultured with gold nanoparticles. On the premise that cells are not affected by the toxicity of gold nanoparticles, gastric cancer cells incubated with gold nanoparticles are irradiated using a nanosecond-pulsed laser with different energies. Propidium iodide and calcein-AM are used for staining verification of perforated cells. The results indicate that optoporation of cell membrane can be successfully achieved with 400 nanoparticles (diameter of 100 nm) per cell and 20 mJ/cm 2 energy density by 532 nm pulsed laser, without obvious dead cells. During the optoporation, the membrane potential is measured using optical mapping technique. It is found that the membrane potential firstly increases and then restores with 50 mV maximum increment and 250 s recovery time. These results confirm that the cell membrane damage can be recovered by optoporation and characteristiced by membrane potential change.