Absorption heat pumps and absorption heat exchangers play an important role in the district heating in China. However, the structure of existing systems leads to weaknesses such as low heat transfer performance and large areas. A detachable plate-type falling film heat and mass exchanger (HMX) couple utilizing lithium bromide (LiBr) and water as working fluids are proposed to address these problems. The performance of the first-generation prototype left room for improvement, with the overall heat transfer coefficient ranging from 0.4 to 0.7 kW·m⁻²·K⁻¹ under generator-condenser conditions. In addition, working conditions could not be established under absorber-evaporator conditions. Optimization of the structure of the liquid distributor in the heat exchanger is also accomplished through this research. The overall wetting rate of the heat exchange plate exceeds 90% during the design flow rate. The liquid distributor for the first-generation prototype is optimized using this method, and the performance of the system is tested. The average heat transfer coefficient of condenser rises to the level of 1 kW·m⁻²·K⁻¹ during the generator-condenser condition. Furthermore, the absorber-evaporator condition can be established, wherein the heat transfer coefficient of the absorber ranges from 0.235 to 0.422 kW·m⁻²·K⁻¹. The results of the improved HMX couple improve the feasibility of this system, reduce the size of the AHP system, and improve the heat transfer performance.