The invention discloses a corrugated sheet structure for a welded plate type heat exchanger, which comprises distribution diversion regions and heat transfer regions, wherein the upper end and the lower end of the sheet are respectively provided with a triangular distribution diversion region; the middle part is provided with a rectangular heat transfer region; the sheet corrugations in the rectangular heat transfer region are composed of main corrugations and auxiliary corrugations; when the sheets are assembled, no support members are needed between the two sheets; every two sloping sides of the triangular distribution regions far away from the rectangular heat transfer region are welded with each other after the sheets are assembled; the two sides of the sheet are respectively used as the straight flow channels for different media; and the media flow in reverse directions. The invention solves the problems of uneven sheet fluid distribution, difficult design of medium inlet and outlet structures, and the like in the prior welded plate type heat exchanger, so that the welded plate type heat exchanger can be used in the occasions in which media are easily choked and scaled.