The utility model discloses a coal seam gas dynamic dew point control device, comprising a reheating dehydration structure for performing coal seam gas dynamic dew point control and a methanol injection structure, wherein the methanol injection structure is connected with the reheating dehydration structure and is used for injecting methanol into the reheating dehydration structure. Natural gas is treated by a structure that the methanol injection structure is connected with the reheating dehydration structure in series, so that high-efficiency, quick and low-cost development of coal seam gas is realized; short-distance pipe network gas-collecting transportation and distribution of a coal seam gas mining area well site is realized so as to control the coal seam gas dew point; a test device and a production device are integrated; the whole process system is simple; project cost is reduced; the workload of on-site construction is reduced; occupied area and construction period are reduced; the coal seam gas dynamic dew point control device has obvious advantages in actual production application.