Co-pyrolysis of coal and biomass is an important technology to realize the clean and efficient utilization of coal and biomass which can not only alleviate the contradiction between the increasing demand and the decreasing reserves of coal, but also solve the problems caused by low energy density, dispersion and seasonality of biomass. However, equipment corrosion caused by alkali metal volatilization seriously restricts the development of coal and biomass pyrolysis technology. In this paper, the influence factors, migration path, research methods and detection methods of alkali metal migration during the process of coal and biomass pyrolysis were reviewed. A review of domestic and international studies on the migration and transformation of alkali metals during the separate pyrolysis and co-pyrolysis of coal and biomass was presented to thoroughly analyze the migration mechanism of alkali metal during the process of coal and biomass pyrolysis. The effects of pyrolysis temperature, thermal conversion atmosphere, heating rate and raw materials on the migration of alkali metals during the process of co-pyrolysis, the gas-phase release and solid-phase transformation of alkali metals during the process of co-pyrolysis, the research progress of research methods and detection methods of alkali metals were summarized. The further research on the in-situ detection of alkali metals volatilization during co-pyrolysis of coal and biomass was prospected.