Field experiments were carried out to study effects of seawater irrigation on yield compositions and ion distribution of different varieties of Helianthus tuberosus growing in coastal mudflat along semiarid regions in 2005. Results show: (1) Nanyu No. 2 was higher than the others in biomass of the roots and aerial parts, and Nanyu No. 5 and Nanyu No. 3 were taller than the others in all treatments, but the effect on diameter of the main stems of the plants varied sharply with treatment. In the treatment of irrigation with 30% seawater, Nanyu No. 1 was not affected in biomass accumulation in roots and aerial parts, but the others to a varying extent. (2) The plants differed sharply in yield between varieties. Nanyu No. 2 was the highest when irrigated with 30% seawater, and so did they in single tuber weight, total sugar and Inulin content. Nanyu No. 1 and Nanyu No. 2 were the highest in single tuber weight. (3) Concentrations of Cl^- and Na⁺ in roots, stems and leaves of all varieties increased with the seawater concentration, but significant differences did exist between varieties. Na⁺ content was lower in leaves than in roots and stems. Judging by biomass accumulation, yield of tubers, total sugar and Inulin contents in tuber, and ion distribution, Nanyu No. 1 and Nanyu No. 2 were more adaptive to planting in coastal mudflat along semiarid regions with seawater irrigation than other varieties.