The feasibility of using the forward osmosis (FO) process involving brown coal as draw agent to reclaim clean water from dye wastewater is evaluated in this study. It is found that brown coal not only has enough driving force for drawing water from dye wastewater but also can be reconstituted during the FO process, thus resulting in directly usable coal water slurry after appropriate FO time as an energy source equivalent to fossil oil or feedstock for chemical synthesis via gasification. In the FO process, water-drawing effect can significantly enhance the slurryability of brown coal via weakening the moisture holding capacity, decreasing the porosity and achieving the favorable particle size distribution due to the improved grindability. A possible tri-factor water-drawing and reconstitution mechanism of brown coal during the FO process is proposed to explain the effects of FO process on the properties of brown coal. The results indicate that the FO process promises to be a low-cost green process for simultaneous wastewater treatment and preparation of coal water slurry for environmental protection and energy production.