Biotrickling filters (BTFs) for the treatment of hydrophobic volatile organic compounds (VOCs) have long been a research hotspot. For the removal of hydrophobic VOCs, mass transfer has become a core issue, which plays a decisive role in the treatment effect of BTFs. At present, there are few studies on the effect of mass transfer on the removal efficiency of VOCs and lack of systemicity. Aiming at the problem of poor mass transfer performance of hydrophobic VOCs in the biological treatment process, the mass transfer theory and purification mechanism of hydrophobic VOCs in BTFs are analyzed, and the mass transfer characteristics of hydrophobic VOCs such as toluene and styrene in different BTFs are reviewed. At the same time, it points out that the latest research progress such as adding surfactants, upgrading the structure and process of BTFs, and optimizing the process parameters that affect mass transfer will become effective means to solve the mass transfer problems of VOCs, especially hydrophobic VOCs. By solving the mass transfer problem of VOCs, the performance of BTFs can be improved, thereby promoting the development of BTFs mass transfer theory and core technology, promoting the transformation of this technology to application, and solving the problem of harmless disposal of multiple categories of hydrophobic VOCs.