[Objective] The aim of this study was to explore allelopathic effects of the water-extracted crude of cucumber plant parts on seed ger- mination and seedling growth of lettuce (Lactuca sativa L.), cabbage (Brassica pekinensis L.), radish ( Raphanus sativus L.) and scallion (Al- lium fistulosum L.). [Method] The allelopathic effects of different cucumber tissues aqueous extracts were investigated on lettuce, cabbage, radish and scallion using the water-soluble allelopathic principle by seedling bioassay tests. [Result] The trends of inhibitory effects of different cucumber parts increased with increasing extract concentrations. The inhibition effects and the inhibition rate of three aqueous extracts were more significant on root growth than shoot length. Leaf aqueous extracts represented the most exhibited and root aqueous extracts representing the least inhibitory on seed germination, shoot length and root length of lettuce, cabbage, radish and scallion. [Conclusion] This study had pro- vided basis for allelopathic character of different cucumber plant parts.