A type of low speed wind tunnel used in research on forestry protection and its structure, function and principle of the design is introduced. The size of the test segment of the wind tunnel is 1.2 m×1.2 m×1.8 m. The velocity of airflow in the tunnel can be steplessly and steadily controlled between 0～6 m/s. Measurement shows that the airflow field in the test segment is uniform and stable. The low speed wind tunnel is suitable for research on insects, mechanism of transportation and deposition of fine droplets and fire behavior.