Based on the orthogonal test design,a field experiment was carried out in mudflat along the coast of Laizhou, Shandong Province to study coupling effect of salt and fertilizer application on Helianthus tuberosus irrigated with seawater different in concentration.The results show:(1)When the fertilization rate remained the same,no significant difference in yield of tuber and aerial parts of the plant between Treatment W₂(25% seawater)and Treatment W₁(fresh water).Their yields,however, significantly declined by 32% and 76% and by 25% and 60% respectively when the irrigation water contained higher percentage of seawater,50% in Treatment W₃ and 75% in Treatment W₄.In the trials of N fertilization,comparison of Treatment N₃(150 kg hm^-2)with Treatment N₁(0 kg hm^-2)showed that the yields of the former were 77% and 37% higher than that of the latter,respectively,and the yields in Treatment N₄(225 kg hm^-2)were lower than in Treatment N₃,but higher than in Treatment N₂(75 kg hm^-2).In the tests on P fertilization,the yields of tuber and aerial parts were respectively higher 97% and 39% in Treatment P₃(60 kg hm^-2)than in Treatment P₁(0 kg hm^-2),and they were lower 19% and 11% lower,respectively,in Treatment P₄(90 kg hm^-2)than in Treatment P₃(60 kg hm^-2).(2)In all seawater treatments the Helianthus tuberosus.main stem got longer and thicker with the increase in N and P.(3)Analysis of the interactions of seawater,N and P showed that Treatments W₂N₃ and W₂P₃ were the opt imal combinations.The main factor that affected the yields was seawater,and flowed by fertilizers of N and P.And the best combination was W₂N₃P₃.