【Aim】 This study aims to investigate the variations in growth and physiological indices of Aegiceras corniculatum seedlings under different salinity and immersion time gradients. The objective is to explore the salt tolerance, immersion tolerance, and the interactive effects of salinity and immersion on seedling development. 【Method】 This study, based on simulated experiments with mangroves, utilized an automated control system in a greenhouse to simulate semi-diurnal tidal flooding. This study investigated the effects of varying salinities and flooding durations on the growth of A. corniculatum seedlings, with the aim of providing scientific guidance for mangrove restoration and achieving significant practical outcomes. The experiment included ten artificial seawater salinity (CK (0‰), S1 (5‰), S2 (10‰), S3 (15‰), S4 (20‰), S5 (25‰), S6 (30‰), S7 (35‰), S8 (40‰), and S9 (45‰)) and five flooding durations [T1 (4 h·d^-1), T2 (8 h·d^-1), T3 (12 h·d^-1), T4 (16 h·d^-1), and T5 (20 h·d^-1)] gradients. Physiological and biochemical indicators, such as seedling height, basal diameter, net photosynthetic rate, catalase (CAT) and superoxide dismutase (SOD) activities, and malondialdehyde (MDA) content, were measured and analyzed. 【Result】 The findings indicate: (1) Seedlings of A. corniculatum grow best in salinity environments of 10‰-20‰, with complete mortality occurring at salinities of 40‰ and above; (2) Optimal growth occurs with flooding durations of 4-12 h·d^-1, with durations exceeding 12 h·d^-1 causing significant growth inhibition; and (3) The best growth is observed under a combination of 15‰ salinity and 12 h·d^-1 of flooding. 【Conclusion】 The increase in basal diameter and height, as well as the net photosynthetic rate of paulownia seedlings, initially rises and then decreases with increasing salinity. With prolonged flooding, these parameters initially increased and then decreased. CAT and SOD activities, and MDA content in A. corniculatum seedlings initially decreased and then increased with extended flooding. Similarly, these parameters first decreased and then increased with higher salinity. The optimal conditions for the growth of A. corniculatum seedlings were 12 h of flooding per day and 15‰ salinity. These results provide scientific guidance for mangrove restoration.