[Objective] The effects of substrate water content and super absorbent polymer on the water potential, water use efficiency and transpiration rate of Platycladus orientalis were studied, in order to provide theoretical basis and technical support for the application of super absorbent polymer in vegetation reconstruction and ecological restoration of lead-zinc tailings ponds in areas with different rainfall.[Methods] The test used a quadratic general rotation combination design. The measured indicators included the water potential, net photosynthetic rate, transpiration rate, and water use efficiency of the annual Platycladus orientalis. A regression model between the water potential(ψ) of the leaf, the water use efficiency (WUE), transpiration rate (T_r) and the concentration of super absorbent polymer and substrate water content was fitted.[Results] ① The main effect sequence of the regression model of water potential and transpiration rate was:substrate water content > concentration of super absorbent polymer; the main effect sequence for the regression model of water use efficiency was:concentration of super absorbent polymer > substrate water content. ② When the water potential reached the highest point, the concentration of super absorbent polymer applied was 0.1%, the substrate water content was 19.73%; when the water use efficiency was highest, the concentration of super absorbent polymer applied was 0.1%, the substrate water content is 7.89%; when the transpiration rate was the minimum optimal, the concentration of super absorbent polymer applied was 1%, and the substrate water content was 7.89%.[Conclusion] Low super absorbent polymer application amount (0.1%~0.23%) is beneficial to the extraction of water from the modified lead-zinc tailings matrix, which also promotes the fixation of carbon dioxide in the leaves and improves the water use efficiency.