The invention relates to a process and a device for detecting foreign matters and selecting tobacco leaves before redrying tobacco lamina. The process comprises the steps such as primary dilution conveying, primary foreign matters detection and tobacco leaves selction, primary foreign matters removal, flow buffering and quantitation, secondary dilution conveying, secondary foreign matters detection and tobacco leaves selection, secondary foreign matters removal and tobacco lamina blending, and the process is characterized in that a tobacco lamina material is continuously photographed through a camera and compared with a tobacco lamina stored in a computer, and a blowing system is controlled to be started so as to remove the foreign matters through a signal if the photographed tobacco lamina material is different from that stored in the computer. The device for realizing the process comprises a primary dilution belt, a secondary dilution belt, a primary foreign matter detector, a secondary foreign matter detector, a two-level blowing removal system and a tobacco lamina blending belt. Compared with the prior art, the removal effect of the tobacco lamina foreign matters can be improved, the removal error can be reduced, the purity of the threshed and redried tobacco lamina can be improved, the uniformity and the stability of the flow before redrying the tobacco lamina can be enhanced, the labor density for selecting the tobacco leaves can be alleviated, and the automation level of the production process can be improved.