Abstract: The effects of potassium fertilization on photosynthetic characteristics, yield, economic benefit and quality of cucumber(Jinchun 3)were studied in the solar greenhouse. There were five levels of potassium fertilization, K2O 0, 240, 480, 720 and 960 kg/ha. The results showed that the net photosynthetic rate is highest under the level of K2O 720 kg/ha, while the area and number of leaves are the largest under the level of K2O 240 kg/ha. With the increasing of potassium application rate, photosynthesis of cucumber is increased at first then decreased, and the equation between K rate and net photosynthetic rate is y=-4.160+4.5307x-0.6693x2 (r=0.9470**). The chlorophyll content is increased with the application of potassium fertilizer, and the relation model between chlorophyll SPAD volume and the potassium fertilizer application rate is y=-6.66+7.406x 8-0.97x2(r=0.9836**). It is obvious that with the increasing of potassium fertilizer rate at the early stages, the yield is significantly increased from 14.7% to 53.5%. The highest yield and benefit of cucumber are under the K2O 720 kg/ha fertilization. The fruitbearing stage of cucumber is advanced and prolonged by the fertilizer application, and the quality of cucumber is also improved. Contents of soluble sugar and vitamin C of fruits are increased under the K2O 240-720 kg/ha fertilization, while, the nitrate contents are decreased.