Bub1 is essential for assembling of the functional spindle assembly checkpoint (SAC) to guarantee the correct separation of sister chromatids. Abnormal expression of Bub1 can elevate defects in SAC function, chromosome instability, and the incidence of aneuploidy. Several recent studies indicate that aberrantly expressed Bub1 may promote the tumorigenesisviaregulating cell proliferation, invasion, migration and cancer stem cell activation. Further understanding of the mechanism of Bub1 in malignancy may provide new targeted therapy strategies.