Investigating the intracellular water dynamics within leaves will clarify plant responses to different water conditions and provide a theoretical basis for enhancing water-use efficiency. Detached leaves of Chinese flowering cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) and broccoli (Brassica oleracea L. var. italica Plenck) were used as experimental materials in this study. Electrophysiological parameters of the leaves under saturated and non-saturated conditions were measured, and the intracellular water, nutrient, and energy related indices were calculated according to Nernst equation. The acceleration (a) reflecting the change rate of water transport rate in cells was defined and calculated, and the response characteristics of the two plant species to water were analyzed. The results showed that leaf intracellular metabolic activities of the two plant species were better in the saturated condition than those in non-saturated condition, and electrophysiological parameters could reflect the intrinsic characteristics and potential of the plants. Under saturated water condition, the intracellular water transport rate, electrophysiological ion transport efficiency and low nutrient tolerance of B. campestris were significantly higher than those of B. oleracea, and B. campestris showed high cell metabolic energy and metabolic activity. From non-saturated to saturated condition, the intracellular water transport rate of B. campestris changed rapidly, but the increase rate of intracellular water holding capacity was low, while that of B. oleracea was just the opposite. Therefore, B. campestris exhibited higher water sensitivity compared to B. oleracea.