A gas hot water heating device and a system with heating function are disclosed. The device includes a combustion device (1), an inlet (E) and an outlet (G) of a hot water pipeline (2), an inlet (I) and an outlet (H) of a heating loop (3), and a water tank (4). The device also includes a first heat exchanger (5), a second heat exchanger (6) and a third heat exchanger (7). A flue gas outlet (1-2) of the combustion device (1) is connected with flue gas passages of the first heat exchanger (5) and the second heat exchanger (6) in order and in series. A first water flow passage (5-1) and a second water flow passage (5-2) are arranged in the first heat exchanger (5), and the water tank (4) and the first water flow passage (5-1) of the first heat exchanger (5) are communicated between the inlet (E) and the outlet (G) of the hot water pipeline (2) in series. The second heat exchanger (6) and the third heat exchanger (7) can exchange heat with water in the water tank (4).