Abstract: With the development of the chemical industry, an increasing proportion of synthetic organic compounds detected today in the environment are ionizable. As ionizable organic compounds (IOCs) may exist in the form of molecules and/or ions in the environment, their bioavailabilities in the environment are site-specific. Factors affecting IOCs bioavailabilities in the environment mainly from the angle of their physicochemical adsorption and biological absorption are elaborated. IOCs adsorption to environmental media is mainly influenced by pH. Generally, neutral molecules are more easily absorbed by the medium than ionized ones. Bioavailability of IOCs depends on ionization degree of these compounds and bioaccumulation factor. According to the theory of ion trap, neutral molecules can penetrate plasma membranes more easily than ionized ones. Once neutral molecules enter into cell, the bioavailability of IOCs depends on pH of the cytoplasm, and the effect inside the cells has nothing to do with pH in the outside environment. Compared with the techniques of biological monitoring and model monitoring, the technique of hollow fiber liquid microextraction is more efficient in evaluating bioavailability of IOCs. Besides, in future studies on bioavailability of IOCs, more emphasis should be laid on influences of pH of the environmental media and pH inside the cells.