In order to determine the differences and influence factors of heat transfer characteristics between the open and closed heat source towers under low temperature and high humidity conditions, this study established an experimental platform of heat source tower heat pump. The heat absorption efficiency was defined to evaluate thermodynamic perfectness of heat source tower. Experiments were conducted to study the influences and differences of dry-bulb temperature 2~10℃, solution inlet temperature -10~-2℃, relative humidity 60~100%, air volume 1400~4400 m3/h on heat absorption efficiency of the open and closed heat source towers. The results show that with solution inlet temperature, relative humidity and air volume increasing, heat absorption efficiency increases, While with air inlet temperature increasing, heat absorption efficiency decreases. Solution inlet temperature has the greatest influence on the heat absorption efficiency, while the influence of relative humidity is negligible. The heat absorption efficiency of the open heat source tower is 0.26~0.55, while the closed heat source tower is 0.16~0.35. Under the same conditions, heat absorption efficiency of open heat source tower is about 35% higher than closed heat source tower, and the heat transfer temperature difference is about 1.0-2.0℃ higher than closed heat source tower. The open heat source tower is more suitable for low temperature and high humidity environment in southern region of China, but the solution float and concentration should be comprehensively considered.