The invention relates to the technical field of heat exchange, and discloses a heat exchanger and a heat exchange enhancement method. The heat exchanger comprises a shell side cylinder, tube plates, a tube bundle and baffling grating plates, wherein the tube plates, the tube bundle and the baffling grating plates are installed in the shell side cylinder. The tube bundle penetrates through the baffling grating plates and is fixedly connected with the tube plates at the two ends of the tube bundle, the sections of tubes of the tube bundle are of a polygonal structure, the edges of the tubes of the polygonal structure are chamfered, the baffling grating plates and the tube plates are respectively provided with installation holes and fixing holes, the installation holes and the fixing holes are matched with the tubes in shape, the baffling grating plates are arranged in parallel in the tube side direction, and arch-shaped gratings of the adjacent baffling grating plates are distributed in a staggered mode. When fluid in a shell side flows through the gratings of the baffling grating plates, Karman vortexes are formed, and resistance of the fluid is little during spin flowing, so that flowing speed of a boundary layer is increased, convective heat transfer of the fluid is effectively enhanced, cleaning dead corners do not exist on inner walls of the tubes, and the tubes are easy to clean. Gaps among the tubes of the tube bundle are similar to rectangles, the Venturi effect is achieved, and the heat exchange effect is greatly improved.