Abstract: In order to study the effect of different electrical conductivity (EC) on leaves photosynthetic characteristics, experiment was conducted in Venlo greenhouse at Jiangsu University from September 10th 2009 to June 30th 2011. In the experiment four kinds of nutrient solution with different EC were use to water cucumber and the EC value were 0.036 dS/m, 1.5, 2.2 and 2.5 dS/m, respectively. Moreover, photosynthesis rate, Chlorophyll fluorescence, Chlorophyll content and production with different EC were measured and relationship between among were analyzed. The result showed that electrical conductivity of nutrient solution had a great effect on value of SPAD, maximum photosynthesis rate, initial light use efficiency and electron transport rate of cucumber lower leaves in greenhouse. No significant difference was found between T3 treatment (EC=2.5 dS/m) and T2 treatment (EC=2.2 dS/m) about value of SPAD, maximum photosynthesis rate, initial light use efficiency, electron transport rate and production of Upper and Middle Leaves, but significantly bigger than T0 treatment (EC=0.036.5 dS/m) and T1 treatment (EC=1.5 dS/m). The experimental model among maximum photosynthesis rate and initial light use efficiency and soil plant analysis development of leaves were established. Relationship between photosynthesis rate and electron transport rate was described to power. This research can provide theoretic foundation to nutrient solution management based on leaves photosynthetic rate.