Abstract: For eliminating the shortcomings associated with screening test in threshing and redrying line, such as tobacco degradation and time lag in detection, an online strips sampling and area measurement device was designed by incorporating threshed strips sampling and mechanically thin-layer spreading, image acquisition and computer processing technologies. The results of application showed that the absolute error of the device was below 2%, and detection duration shortened from 30 to about 10 minutes comparing with screening test.