Wind tunnel test has the advantages of convenience, speed and efficiency, and is widely used in wind turbine power characteristics test. When the diameter of the test rotor is large, the test results will be affected by the clogging effect of wind tunnel. The 300W wind turbine was used as the research object, and the output power characteristics test was performed using the wind tunnel test and the vehicle test respectively. The test process used a load method with resistance and the battery as the load. The test was carried out in a test segment with a wind tunnel section of 3m×3m. The no-load starting wind speed of wind turbine is 4.3m/s~4.8m/s. The rated wind speed when the resistance is the load is 6.2 m/s. In the vehicle test, the wind turbine""s no-load starting wind speed is 5.7m/s~6.2m/s, and the rated wind speed when the resistance is the load is 8.1 m/s. The starting wind speed of the wind tunnel test is 1.4m/s lower than that of the vehicle test, accounting for 24.6% of the starting wind speed of the vehicle test, and the rated wind speed of the wind tunnel test is 1.9m/s lower than that of the vehicle test, accounting for 23.5% of the rated wind speed of the vehicle test. The diameter of the rotor is 2.3m,and its swept area accounts for 46.2% of the cross-sectional area of the wind tunnel test section. The clogging effect of the wind tunnel is large, which results in a large difference between the wind tunnel test data and the vehicle test data. so it needs to be corrected after the wind tunnel test.