To further reduce the outlet temperature of the primary water and increase the transmission capacity of the heating pipe network, the series-type supplemental fired absorption heat exchanger was used at the heat station of central heating system to replace the conventional single-segment absorption heat exchanger. In this study, with the technical constraints of feasibility of heat transfer terminal difference considered only, by analyzing the heat transfer process and thermodynamic cycle of each heat transfer component in series-type supplemental fired absorption heat exchanger, the mathematical model of the unit was established and solved by iterative numerical method, and the temperature conditions of primary water inlet, secondary water inlet and outlet satisfying the design requirements of heat exchanger station were quantitatively analyzed. The distribution rules of the minimum temperature of primary water outlet, the maximum heat supply of unit, and the heat transfer in unit were discussed. Research results show that when the temperatures of the primary water inlet was 110℃, the secondary water inlet and outlet were 60/45 ℃, the minimum temperature of the primary water outlet of the supplemental heat exchange unit was 22 ℃. The conveying capacity of the pipe network was 1.76 times of a conventional 110/60 ℃ water-to-water heat exchanger and the heat supply was twice of a conventional water-water heat exchanger. For conventional single-stage absorption heat exchangers, the primary and secondary water supply temperatures had little effects on the expansion coefficient, which was about 1.5. When the primary water inlet temperature was 100 ℃ and the secondary water inlet/outlet temperature was 69/54 ℃, the maximum expansion coefficient of the supplementary combustion absorption heat exchanger was about 3.3.