The invention relates to a self-vibration preventing device for a pit heat transfer tube. The device comprises the pit heat transfer tube, a flat nut, a hoop and a baffle plate. The hoop externally sleeves the pit heat transfer tube, the flat nut is matched at the left end of the hoop, and the right end of the hoop is mounted in a cone-shaped hole of the baffle plate. During work, the pit heat transfer tube can be tightly matched with the porous wall of the baffle plate, so that a fluid induced vibrating frequency is far from the frequency of the heat transfer tube, the problems of vibration, collision, abrasion and the like of the pit heat transfer tube are solved, the supporting action on the pit heat transfer tube by the baffle plate is enhanced, and the pit heat transfer tube is prevented from being bent. Compared with the prior art, the device is simple structure and convenient to mount, detach and maintain.