A small scaled seed circulating dryer and an induced-draft drying process system were developed by analyzing physical properties of seeds and objective potential energy of drying systems. A kind of proportional valve was designed to eliminate thermal inertia of dryer thermal (the ratio of exhaust gas to hot air) and an adaptive control system was developed base on the relationship between seed moisture and drying process by using the proportional valve. To ensure the reliability of the drying machine cleaning, a delivery flap, which could rotate 360°, was designed to clean up the dryer and realize step-less delivery. The result showed that the drying temperature was lower than the traditional drum wind dryers by 9℃, and the drying efficiency was increased at least by 20%, and no seeds were leave over after delivering.