Abstract: The temperature was controled in the plastic greenhouse cooling by some cooling measures, which were water-loop heat pump, outside shading, inside sprayed cooling shading and mechanical forced ventilation, while cucumber was grown in summer. The results show: the coefficient of performance of the water-loop heat pump used in the experiment was 3.38. The contribution ratios for the outside shading and the forced ventilation to cool the greenhouse were 59.35% and 9.2% respectively. The contribution ratio for the water-loop heat pump and inside sprayed cooling shading to cool the greenhouse was 31.5% and the average temperature inside greenhouse was 1.0℃ lower than the outside when the actual cooling power of the water-loop heat pump was 157.5 W/m². While the pump worked at noon, the horizontal distribution of temperature was uniform in the east-west direction of the compartment. However，there was a temperature difference of 1.7℃ covering a 15.0 m distance in the south-north direction 1.5-m above the ground and there was a vertical difference of 1.6℃ at 2.0 m above the ground. Cucumber grew well in the greenhouse. When greenhouse was designed to be heated and cooled by water-loop heat pump, the cooling power of the water-loop heat pump should first be suitable for cooling requirement in summer because heating load of greenhouse in winter is lower than cooling load in summer.