Abstract: Halophila beccarii is listed as vulnerable (VU) species on the IUCN Red List. The rapid reduction in area of seagrass bed of H. beccarii has received widespread attention in recent years, and the germination and growth of its seeds are important for large-scale restoration of damaged seagrass beds. To investigate the key environmental conditions during initial population establishment phase of H. beccarii, we combined field experiments with laboratory cultivation for the study. We comparatively analyzed the effects of different temperatures, salinities, sulfide concentrations, and seed burial depths on the seed germination and seedling growth of H. beccarii. Results indicate that the optimal combination for the seed germination is muddy sediment type under temperature 20 ℃, salinity 5 and sulfide concentration 30 μmol/L at burial depth of 2 cm. Under the condition, the seed germination rate reached 35.00% in 60 days and 73.33% in 90 days. The optimum temperatures for both seed germination and seedling growth were 20 ℃ to 30 ℃. Salinities between 5 and 15 were favored for seedling survival and growth. High sulfide concentrations inhibited seed germination. Excessive burial depth suppressed seed germination, with the optimal range for seedling growth being 1 cm to 3 cm. Studying the environmental factors affecting seed germination and seedling growth of H. beccarii not only helps to understand the long-term ecological adaptations, but also provides important practical significance for predicting population regeneration and formulating restoration strategies.