The paper Inspects the Bcl-2 and Bax protein expressions in vivo Wistar mice cells stimulated by steep pulse field, and puts forward the mechanism of steep pulse inducing apoptosis. Bcl-2/Baxprotein expression positive rate and apoptotic cell rate are determined by using immunohistochemical technique and TUNEL in 18 Wistar mice transplanted with Walker-256 cell line. Compared with control group, protein expressions of Bcl-2 and Bax in treated group decrease and increaserespectively. Apoptosis occurrswhen tumor tissue are impulsed by steep pulse field.