To provide a dehydration system of low-grade coal, capable of reducing the amount of a used dehydrating agent.

A dehydration system of low-grade coal has a chemical dehydration system (C) for bringing the low-grade coal into contact with a liquefied product of a dehydrating agent to allow the water contained in the low-grade coal to be dissolved in the dehydrating agent to afford a mixture of the water with the dehydrating agent, and to dehydrate the low-grade coal, recovering the dehydrating agent in a gas state by subjecting the mixture to gas-water separation to separate the mixture into the dehydrating agent in a gas state and the water, liquefying the recovered gas-state dehydrating agent by one method of pressurizing, cooling or both of the pressurizing and cooling, and reusing the liquefied dehydrating agent for the dehydration of the low-grade coal, and a mechanical dehydration system (B) installed in the upstream side of the chemical dehydration system, mechanically dehydrating the whole or a part of the bulk water included in the low-grade coal, and feeding the dehydrated low-grade coal to the chemical dehydration system.