A method and device are provided for purifying and recycling water vapor from a coal drying process. Included are a temperature-lowering and dehumidifying process, a flash distillation stripping process, and a vacuum condensing process. A condensing tower receives a temperature-lowered exhaust gas with high humidity from a cooling tube and a condensed water of 5˜60° C. from a flash distillation tank, allowing the exhaust gas and the condensed water to contact each other in a vapor-liquid reverse manner, to lower the temperature and dehumidify the exhaust gas. The flash distillation tank performs a vacuum flash distillation to the condensing water pumped therein from the condensing tower. Water vapor of 5˜60° C. evaporated through flash distillation in the flash distillation tank enters into the demisting washer to be dehumidified and then is condensed. The condensed water in the vapor condenser is transferred into a recycled water tank. Non-condensable gas is discharged out.