This paper studies the apoptosis of human ovarian carcinoma cell Line (SKOV3) induced by the nanosecond pulsed electric field (10kV/cm, 100ns, 1 Hz) and its effect on intracellular calcium concentration ([Ca2+]i). These cells were doubly marked by Annexin V-FITC/PI, and the apoptosis rate was analyzed with flow cytometry. After AO/EB staining the morphological changes were observed under fluorescent microscope, and their ultrastructural changes were observed under scanning electron microscope (SEM). With Fluo-3/AM as calcium fluorescent marker, laser scanning confocal microscope (LSCM) was used to detect the effect of nsPEF on [Ca2+]i and the source of Ca2+. The results showed that the early apoptosis rate of the treatment group was (22.21+/-2.71)%, significantly higher than that of the control group (3.04+/-0.44)% (P<0.01). The typical features of apoptotic cell have been observed by fluorescent microscope and SEM. It is proved that nsPEF can induce apoptosis of SKOV3 cells and result in distinct increase in [Ca2+]i (P0.01), which was independent of extracellular calcium concentration (P>0.05). Since nsPEF can penetrate cell membrane due to its high frequency components, one of the mechanisms of nsPEF-induced apoptosis may be that activating intracellular calcium stores can increase the [Ca2+]i, and consequently, the apoptotic signal pathway can be induced.