Three uptake experiments were performed under laboratory conditions: (1)Phosphate uptake kinetics of macroalga, Sargassum horneri, between 5-25℃;(2)Effect of N:P ratio on the uptake of N and P by S.horneri; (3)Effect of NH₄⁺-N/NO₃^--N ratio on the uptake of N and P by S.horneri.The results were: (1)The maximum absorption rate(V_max)rises with temperature variation between 5-20℃,and reaches the max at 20℃; The half saturated absorption constant (K_m) decreases with temperature variation between 5-20℃, and reaches the min at 20℃; (2)when the N concentration was constant, the uptake rate of N and P decreases with the N:P ratio variation between 16:1 to 256:1; While the P concentration was constant, the uptake rate of N rises, and P decreases with the variation of N:P ratio.(3)when phosphate is adequate, the uptake rate of NO₃^--N has a negative relation with NH₄⁺-N/NO₃^--N, while NH₄⁺-N and P have a positive relation with NH₄⁺-N/NO₃^--N variation between 1:1-8:1, and a negative relation with that above 16:1.(4)The TN and TP in S.horneri are 5.70% and 0.18%, respectively.