In the present work, an experimental study was conducted to determine the ignition characteristics of wheat flour and provender (mainly cotton seed residual) dusts, Experiments were conducted in a horizontal shock tube, with a new technique for distributing the dusts. Samples with different shapes and the same volumes are suspended in the centre of the shock tube, and the shock wave is responsible for disperson of the dusts. The ignition delay time of the aforementioned dusts, based on the pressure rise criterion, has been measured. Experimental results show the influence of dust concentration on the ignition pressure difference, and the ignition delay time. In addition, the effect of the sample shapes on ignition delay time is shown. Kinetic constants of grain dusts are also estimated by using the experimental results. The flammability limits and concentration at optimum conditions for these dusts are determined.