Abstract: In order to separate grain by airflow, the inertia deposition separation chamber was designed for 4ZTL-1800 rice combine harvester threshing prior to cutting with air suction. To further study the work mechanisms of the chamber, experimental study using high speed video camera system (HSVCS) was made on the process of grain moving in the inertia deposition separation chamber. The result was analyzed quantificationally. The laws of grain depositing and light grain cleaning were obtained. The results can provide theoretical basis to further increase working efficiency of the inertia deposition separation chamber.