The utility model discloses an inlet air automatic control system of a biomass furnace. The inlet air automatic control system comprises a heating chamber and a baking chamber, wherein the heating chamber is communicated with the baking chamber by upper and lower air flues; a heating furnace is arranged on the inner part of the heating chamber; and an air blower is arranged on the outer part of the heating chamber; the inlet air automatic control system is characterized in that an air outlet of the air blower is connected to an air inlet of an air box, wherein a plurality of air inlet tubes are further arranged at the other side of the air box; the air inlet tubes are communicated with the air box and the heating furnace; solenoid valves for controlling the supply air rate are arranged on the air inlet tubes respectively; the solenoid valves are connected to a main controller by a signal transmission wire; a temperature sensor is arranged on the inner part of the baking chamber; and the sensor is connected to the main controller by the signal transmission wire. The inlet air automatic control system of the biomass furnace disclosed by the utility model can be used for automatically adjusting the supply air rate in the heating furnace, has the advantages of being good in temperature control effect, convenient to operate and the like, and is remarkable in improving the quality effect of flue-cured tobaccos.