Abstract: Coal pyrolysis is the initial and necessary stage in the thermal transformation and utilization of coal. The coal gas,tar,and semi-coke products is produced by thermal decomposition of coal. It is an important source of chemical industrial feedstocks and energy fuels in China,so it is of great significance to study the pyrolysis characteristics of coal for the directional control of coal conversion process. Primary pyrolysis is one of the important steps in the coal pyrolysis process,most of the coal pyrolysis products originate directly or indirectly from the primary pyrolysis,and the yield and properties of the primary pyrolysis products directly affect the targeted regulation of the secondary pyrolysis on the target products,so the secondary regulation has certain limitations in improving the yield of coal pyrolysis products.The concept of coal in situ pyrolysis was proposed in the paper,in order to improve the yield of coal pyrolysis products. From the perspective of directly affecting the primary pyrolysis of coal,the different pretreatment methods for coal,including thermal pretreatment and hydrothermal pretreatment,solvent swelling pretreatment,ionic liquid pretreatment,and swelling simultaneous loading metal ion pretreatment were summarized,and the process parameters such as temperature,pressure,pyrolysis atmosphere,residence time,and particle size were reviewed on the in-situ pyrolysis of coal. Finally,the future development trend of coal pyrolysis technology was prospected. On the basis of continuing to explore the mechanism of coal pyrolysis,how to combine the advantages of different coal pretreatment methods and different process parameters is a question. The corresponding coal pyrolysis technology is developed to increase the yield of coal in situ pyrolysis and reduce environmental pollution.