In this study, the 2yearold seedlings of Calamus tetradactylus were selected as the research object. Through the control experiment, we set four light intensity gradients—S0 (control, full light), S1 (75% to 80% full light), S2 (45% to 50% full light), and S3 (20% to 25% full light), and three water gradientsW0 (control, RSWC 85%), W1 (moderate drought, RSWC 55%), W2 (severe drought, RSWC 25%), on a regular basis to determine seedling growth characteristics (plant height, ground diameter, leaf number), photosynthetic capacity ［net photosynthetic rate (P_n), transpiration rate (T_r), intercellular CO₂ concentration (C_i), stomatal conductance (G_s)］ and absorptive capacity (root, stem and leaf biomass), and path analysis using structural equation model, to explore the pathway of light and water on the growth characteristics of C. tetradactylus seedlings, and to provide theoretical support for seedling cultivation and resource restoration. The results show that: (1) with the decrease of light intensities, the growth characteristics, absorption capacity and photosynthetic capacity of seedlings showed a consistent change trend, increased firstly and then decreased. (2) With the decrease of soil water content, the growth characteristics, stem and leaf biomass of seedlings decreased gradually, while the ratio of root and root crown increased firstly and then decreased. In terms of photosynthetic capacity, P_n, C_i and T_r were significantly reduced by 23.65%, 20.61% and 25.40% compared to the control group (P < 0.05). G_s and WUE were increased but not significantly different from the control group (P > 0.05), and L_s was significantly increased by 170.00% compared to the control group (P < 0.05). (3) Structural equation model analysis showed that light could affect the photosynthetic capacity of seedling leaves and water could affect the growth characteristics of seedlings by affecting the root biomass. This study shows that SEM model can effectively analyze the environmental factors that affect the growth of C. tetradactylus seedlings, and quantitatively explain the path process affected by environmental factors. Light and water transfer influence on growth characteristics through photosynthetic capacity and absorption capacity, and the influence of light factor is greater than that of water factor, with path coefficients of 0.89 and 0.56, respectively. During the cultivation of C. tetradactylus seedlings, the standard factor load of ground diameter was 0.85, which could effectively reflect the growth characteristics of C. tetradactylus seedlings. The seedlings grew best under moderate shade (45%-50%) plus normal water supply (RSWC 85%).