During grain storage and processing, aeration and drying are often conducted to control grain temperature and moisture content. To reduce energy consumption and reach the desired drying and aeration effect, the system must be optimized. The factor most influencing the system optimization is the airflow resistance which is influenced by porosity and touristy of the grain bulks. Dockage size and percentage influence the porosity and touristy. In this study, a cubic chamber (inner dimensions: 50×50×50 cm3) was used to measure the airflow resistance (pressure drop) of wheat mixtures with different sizes (≤1.1 mm, 1.1-2.0 mm and ≥ 3.3 mm) and percentages (0, 1.0, 2.5 and 5.0%) of dockage and different moisture contents (14.5, 16.5 and 18.5%) under different airflow velocities (1.1 to 6.6 m.s-1) and airflow directions (vertical and horizontal directions). The air velocity inside the wheat mixtures was directly measured at six locations by using Pitot tubes. In wheat mixtures with any dockage percentages and sizes, pressure drop decreased with the decrease of airflow velocity in both vertical and horizontal directions. Adding 1 to 5 Kg of fine materials (≤1.1 mm) into 100 Kg of clean wheat led to an average increase of 30% for airflow resistance in the vertical direction and 50% in the horizontal direction. Dockage size of 1.1 to 2 mm did not affect pressure drop. Chaff (≥ 3.3) could decrease the airflow resistance, while adding 2.5 percentage points of chaff only resulted in less than 25.9 percentage point reduction of pressure drop. The mixed size of 7.5% dockage had an average 45.6 and 41.2 percent point increase of pressure drops in horizontal and vertical directions, respectively. Pressure drop in the vertical direction was approximately 50% more compared to those observed in the horizontal direction for any moisture content of wheat. The increase in resistance could be 100% higher and depended on the percentage of dockage, dockage size, and dockage distribution. Increasing two percentage points of moisture content reduced the airflow resistance by about 10 to 20% in any airflow direction. The best equation predicting airflow resistance was Modified Haque equation.