The machine is the first small continuous and circulating grain dryer with national patent (Patent No.: ZL 201320646470.6). The machine can use different drying processes flexibly according to different moisture level of grains to improve drying efficiency, save energy and ensure the grain quality after drying. Use continuous drying process for low-moisture raw grain which will be discharged directly after dried for the first time. Use circulating drying process for high-moisture raw grain which will be circulated into the dryer with the circulating delivery system for the second drying. The moisture level of grain will be tested in real time at the exit of dryer. Until the safe-moisture level is reached, will the discharge valve be started to discharge grain out of the dryer.