The invention provides a multifunctional flat-plate heat exchanger which comprises a heat-exchanging flat plate, a spectral-selectivity absorption layer, a light transmitting layer, at least one heat conducting structure and at least one airflow driving device. The heat-exchanging flat plate is provided with a first plate surface and a second plate surface in opposite, and further provided with a pipeline arranged between the first plate surface and the second plate surface. The pipeline is arranged for a heat-conducting medium to flow therein. The spectral-selectivity absorption layer covers the first plate surface. The light transmitting layer covers the spectral-selectivity absorption layer, and the light transmitting layer and the first plate surface are arranged on two opposite sides of the spectral-selectivity absorption layer. The heat conducting structure is arranged on the second plate surface, and defines at least one runner with the second plate surface, and is provided with multiple first through holes communicated with the runners. The airflow driving device is arranged on one side of the heat-exchanging flat plate and the heat conducting structure by corresponding to the runners, is used for driving external air to flow into the runners to or driving internal air to flow to the outside.