Abstract: Under water culture, this paper researched into the effect of copper stress on photosynthesis and nutrient absorption of grafted (Cucumis sativus L. “Xintaimici” / Cucurbita ficifolia) and ungrated cucumber. Under 6 days of copper stress, there is significant depression in the contents of chlorophyll, carotenoid, nutrient(N, K, Ca, and Mg), and in net photosynthetic rate and stomatal conductance in both grafted and ungrafted cucumber seedling leaves. An obvious increase in electrolyte leakage is also observed. Though intercellular CO₂ concentration depresses with increase in Cu concentration, there exists no significant correlation among the treatments. The contents of chlorophyll, carotenoid and nutrient (N, K, Ca, and Mg) and the net photosynthetic rate of grafted cucumber seedling leaves are significantly higher than those in ungrafted cucumber plants. On the other hand, percent electrolyte leakage is significantly lower in grafted than that in ungrafted cucumber plants. Copper content in grafted cucumber seedling leaves is significantly lower than that in ungrafted seedling leaves. This implies that grafted cucumber plants have the strong capacity for inhibiting Cu²⁺ accumulation in leaves which alleviates copper poison.