In order to investigate the mechanisms of phenylhexyl isothiocyanate (PHI) inhibiting the proliferation of multiple myeloma cell RPMI8226 in vitro, the RPMI8226 cells were co-cultured with PHI of various concentrations. The inhibition of proliferation was measured by MTT test and the cell apoptosis was assayed by DAPI staining. The changes of Notch1, Jagged2, BCL-2 and p-Akt proteins in the PHI-treated cells were detected by Western blot. The results showed that PHI inhibited RPMI8226 cell proliferation in certain concentration range and induced their apoptosis. The inhibiting effect caused by PHI showed a concentration-and time-dependent manner. The PHI decreased expressions of Notch1 and Jagged2 proteins in a concentration-and time-dependent manners, the levels of BCL-2 and p-Akt declined at the same time. It is concluded that PHI can inhibit proliferation of RPMI8226 cells, and induce their apoptosis. The cell apoptosis is associated with the inhibition of Notch signaling and downstream targets BCL-2 and p-Akt proteins of RPMI8226 cells, PHI may be a new Notch signaling inhibitor and a promising therapeutic drug for multiple myeloma.