The invention discloses a tail gas heat recovery device with a controllable heat exchange amount and an operating method thereof. The tail gas heat recovery device comprises a gas inlet pipe and an exhaust pipe, wherein the tail end of the gas inlet pipe is divided into a heat exchange passage and an exhaust passage which are combined at the exhaust pipe; a flow control valve is arranged at the separation part of two passages; the middle section of the heat exchange passage is an inflated gas chamber; one end of a heat pipe is inserted into the gas chamber, and the other end of the heat pipe is inserted into a liquid collection tank; two ends of the liquid collection tank are respectively provided with a liquid inlet pipe and a liquid exhaust pipe. When a heat utilization part utilizes much energy, the control valve sends out a control signal, so that tail gas shunted by the heat exchange passage is increased or all the tail gas passes through the heat exchange passage; when the heat utilization part utilizes less energy or a heat exchanger is not needed to supply thermal energy, the control valve sends out a control signal, so that the tail gas shunted by the heat exchange passage is reduced or all the tail gas passes through the exhaust passage. By virtue of the dual-passage structure of the device, control over the heat exchange amount is realized, and the device has relatively extensive application occasions.