The coherence between the two lower levels via incoherent pumping of these two levels to a fourth auxiliary level is considered to investigate the optical bistability in unidirection ring cavity with a lower level doublet atomic sample. It is shown that the optical bistability can be controlled via the interference of incoherent pump processes. It is discovered that the incoherent pump field can even lead to multistability. The optical bistability can be controlled by choosing the appropriate parameters.