Optical coherence bistability (transverse optical bistability) arised from the nonlinear modulation of coherence and its experiment arrangement is first reported in this paper. Calculation and theoretic analysis show that many kind of optical bistability can be obtained in different conditions such as γ/ν or ν/v feedback, with orosscoupling between two dimension coherence signal or without coupling. The stable stable state equations, appropriate parameter range and switch conditions in several situation are given. This kind of optioal bistability may be used in picture enco:iingy optioal oalonlation. and quan bfioation of degree of spatial coherence.