Abstract: Due to the problems of environmental pollution and energy loss caused by loose and friable lignite after upgrading, during transport, the main forming co nditions of lignite after upgrading, such as forming water and coal particle size were analyzed, and combined with self-developed single cylinder hydraulic forming devic e of lignite, the experimental study of forming water content and particle size distribution were separately carried out. The results showed that the forming water and cO al gradation were more conducive to improve lignite after upgrading forming, which provided experimental evidence and theoretical reference of low-cost forming conditi ons of lignite after upgrading.