Abstract: The airflow pressure field in the cleaning chamber of the traditional grain winnowing device is irregular, and is not applicable on occasions where high cleaning efficiency is required. Meanwhile, the centrifugal blower is hard to use to obtain a wide and steady wind source. Therefore, a cross-flow grain cleaning device was designed by employing the cross flow blower that is theoretically distributed evenly in the direction parallel to the blower shaft no matter how wide the blower is. And a horn-shaped airflow expansion channel was designed to increase the height of the blowing area. A feeding hopper and two feeding rollers were installed above the cleaning chamber to extrude the materials into a thin layer and accelerate the material layer to a certain speed. Based on the standard K-ε turbulent model and particle dispersed phase model, the characteristics of a gas-solid two-phase flow in the developed cleaning chamber were numerically simulated. The airflow model was developed by setting the inlet of the airflow expansion channel as the velocity inlet boundary, the outlet of the cleaning chamber as the outflow boundary, and the others as wall boundaries. The unstructured tetrahedral grid was applied to mesh the cleaning chamber model in Gambit. And by making the assumptions on the grain components which mainly consisted of gravel, whole grain, immature grain, and short stems: 1) All particles were modeled as equivalent spheres; 2) There was no interaction between particles; 3) There was neither heat nor mass transmission between particles and the gas phase, and the bidirectional coupling Lagrangian scheme was utilized to trace the particles' movement. Finaly, the distribution of airflow velocity and the particle trajectory was simulated after setting the airflow velocity at the blower outlet and the material parameters. The simulation results indicated that the airflow in the cleaning chamber presented a certain delamination where the airflow near the top and bottom walls had lower velocity than that passing through the mid-chamber and the airflow distribution in each layer was stable without an obvious vortex. Each grain component had respective particle trajectory and was distributed at the bottom of the cleaning chamber in different arc-shaped areas which should be due to the high airflow velocity near the front and back sides and low airflow velocity in the middle of the cleaning chamber caused by the inward-incline of the front and back side boards of the airflow expansion channel. A test rig of the cross-flow grain cleaning device was built to verify the numerical simulation results of the gas-solid two-phase flow in the cross-flow grain cleaning device. A high-speed photographing system was used to record the motion graphics of the whole grains, short stems, and immature grains at a rate of 250 fps respectively. Then the trajectory of each component was identified by the graphic processing. The experiment results showed that the distribution area of the whole grain in the cleaning chamber did not overlap with that of the impurities. The trajectories of the short stems and immature grain were found to partly overlap in the experiment that was different from the simulation. The main reason for this phenomenon was that the short stems were modeled as an equivalent sphere in the gas-solid two-phase flow model. However both simulation and experiment results demonstrate that the whole grain could be separated from the impurities effectively in the developed cross-flow grain-cleaning device.