Abstract: The present invention relates to an anti-paper jam protection device for shredders comprising a paper thickness detecting device, an indicating device and a controlling device, wherein the paper thickness detecting device is an electromagnetic induction paper thickness detecting device comprising a contact element, an electromagnetic element and an electromagnetic induction element, the contact element is connected rotatably to the body of the shredder, one end of which is positioned in the paper inserting passage, on the other end of which is mounted the electromagnetic element, the electromagnetic induction element is mounted on the body of the shredder and spaced with the electromagnetic element face to face, and the controlling device is in line connection with the electromagnetic induction element, the present invention controls the thickness of the paper to be shredded during the paper inserting stage, and shreds paper automatically only in a predetermined value range, to avoid abnormalities that result