Under ebb-and-flow irrigation system，taking cucumber variety ‘Zhongnong No.18’ as material，this study carried out plug seedling culture in summer and winter，and compared the effects of different irrigation height（1 cm，2 cm and 3 cm）on water absorption rate of substrate，growth indexes of cucumber plug seedlings，root system vigor，and water and nitrogen use efficiency．The results showed that the water absorption rate of substrate accelerated gradually along with the irrigation height increasing．In summer and winter，when irrigation heights were 2 cm and 3 cm，the plug seedling height，leaf area，shoot fresh weight and dry mass were all higher than the 1 cm irrigation height，while the indexes of root volume，root system fresh weight and dry mass，root-shoot ratio and strong seedling index showed no significant differences among the 3 irrigation heights．However，the root system activity of plug seedlings at 3 cm irrigation height was significantly decreased，and the volume of feed and return liquid and application amount of fertilizer were the largest．In summer，the water and nitrogen use efficiency of plug seedlings was the highest under 2 cm irrigation height．Based on the growth indexes and water/fertilizer use efficiency of plug seedlings，in summer and winter，the suitable irrigation height was 2 cm for cucumber plug seedlings under ebb-and-flow irrigation．