A novel measurement method for coal thermoplasticity was developed, where permeation distance of thermally plastic coal into glass beads layer placed on the coal sample was measured. The characteristic of this method is simulating the condition in a coke oven, especially void structure around the plastic layer by using glass beads and coking pressure by applying a load. In a standard condition, the coal sample is heated to 550 °C, and coal sample softens and permeates into the glass beads layer, then the permeation distance is measured after cooling the sample. The maximum permeation distance measured is roughly correlated with Gieseler fluidity, however large deviation is observed especially for high fluidity coals. Moreover, the deterioration of coke strength is observed in case that long permeation distance coal is used in a coal blend for cokemaking. This new measurement method clearly shows the difference in coking property of high fluidity coal as well as solving the problems in Gieseler plastometer method for evaluating high fluidity coals. By employing the permeation distance method, contribution to the production of high strength coke and effective usage of caking coal will be expected.