Compling a program by matlab to investigate closed heat source tower operating under spraying conditions. The numerical results of the spray solution temperature, the refrigerant temperature, air enthalpy value were compared with the experimental ones. The program was used to calculate the distribution of the spray temperature, refrigerant temperature, air enthalpy in the closed heat source tower under spraying conditions. Some results were obtained. The air enthalpy is linear distribution and upper fin heat exchanger heat transfer effect is better than the lower part.The center of the tower is firstly frosting. The air dry bulb temperature is above 5.1 ℃and relative humidity is above 75%. The closed heat source heat pump system is without risk of frost, so stopping the spray pump is viable in order to reduce the energy consumption of the operation of the heat pump system.