The invention provides a coal pyrolysis method, which comprises the following steps of: a) crushing raw coal comprising brown coal into the first powdered coal with the mean particle size of 1.5 to 3.5mm; b) drying the first powdered coal in a drying device by one step to prepare the second powdered coal with the water content of less than or equal to 2.5 weight percent at the temperature of between 80 and 100 DEG C, wherein the axial inclination of the drying device during drying is 15 degrees; and c) mixing the second powdered coal and coal ash and performing pyrolysis reaction in a pyrolysis reactor so as to prepare a first gas product and a first solid product. By pretreating the brown coal in the coal pyrolysis method, the second powdered coal of which the granularity, temperature and water content meet the requirements is directly obtained, and the second powdered coal can directly undergo the coal pyrolysis reaction; and in the process, by crushing the coal into the granularitywhich meets the proper requirement, the coal pyrolysis method has the advantages of capacity of avoiding deep drying from generating more fine ash in the drying process, contribution to reducing the energy consumption and simplifying the technology, and capacity of improving the utilization effect of the brown coal.