By taking the ground sections (stems, leaves) and underground sections (roots) of Acanthus ilicifolius as the donors, the Sonneratia apetala seeds as the receptors, and adopting indoor hydroponic cultivation method, the allelopathy of A. ilicifolius to S.apetala was evaluated with the indexes system, including germination ability(germination rates, simplified vitality index, root sprouting rate, field germination) and seedling quality (seedling plant fresh weight, water content, seedling length and seedling root length). The results show that the two parts of the Acanthus ilicifolius (stems, leaves)all had allelopathic influence on S.apetala, the intensity of aerial parts were greater than the underground sections, each part of the interaction strength increased with increase of concentration; the influence of germination, except the underground sections 0.1g · ml-1 , could promote the sprouting root speed, the rest showed a significant and very significant inhibitory effect, ground sections 0.4 g · ml-1, 0.5 g · ml-1 group, field germination were 40/% and 0%; in the aspect of impact on the quality of the seedlings, Acanthus ilicifolius emerged two very significant laws, nemaly "high concentrations inhibit and low concentrations promote" , the water content decreased with increase of two part' s concentrations.