The invention relates to an automatic compressing fixture for radiating plates. The automatic compressing fixture is used for automatically compressing and positioning the radiating plates when the radiating plates are welded. The automatic compressing fixture is characterized in that a cylinder is fixed onto a frame, a cylinder connector is fixed to an end of a piston rod of the cylinder, and a clamping cylinder is fixed onto the cylinder connector; a bottom plate is fixed to the top of the frame, a center shaft is slidably inserted in the bottom plate, a positioning pressure plate is fixed onto the center shaft, and a centering plate is arranged on the center shaft and is positioned between the bottom plate and the positioning pressure plate. The radiating plates can be quickly and stably compressed and positioned by the automatic compressing fixture, and the automatic compressing fixture can work stably and reliably, and has the advantages of simple structure, small size, convenience in use, and the like.