A recovery system of waste heat from flue gas. The system includes a first heat exchanger and a second exchanger. The first heat exchanger includes a heat absorption section, a heat release section, and a first pipeline. The second heat exchanger includes a second pipeline including an inlet header and an outlet header. The system further includes a third pipeline. The first heat exchanger is disposed at a relatively high temperature side of a flue, the second heat exchanger is disposed at a relatively low temperature side of the flue, and the first heat exchanger and the second heat exchanger are connected by the third pipeline. The heat absorption section and the heat release section are connected by the first pipeline to form a circulation loop; the heat absorption section is disposed in the flue; the heat release section is disposed in the third pipeline.