The filaments of Scytosiphon lomentaria preserved in our laboratory were used as the experimental material, and the effects of five culture media L1, PES, F1, f/2 and ESNW on the growth and development of filaments of S.lomentaria were studied, meanwhile, the effects of the different concentrations of nitrate and phosphate based on NO₃^--N and PO₄^3--P free of L1 culture medium on the growth and development of filaments of S.lomentaria were also studied by the experimental ecology methods in this paper.Results showed as follows:(1)L1 was the optimal culture medium for the growth and development of filaments of S.lomentaria in the five culture media.The filaments of S.lomentaria were dark brown and the cytoplasm was plentiful cultured in L1 medium, the increasing ratio of filament biomass was(560.48%±0.73%), the sporangial branchlets ratio and the sporangium diameter could reach up to(46.88%±0.41%)and(18.95±0.89)μm, respectively, after being cultured for 28 days in L1 culture medium;(2)The optimal concentration of NO₃^--N for the growth and development of filaments of S.lomentaria was 6.00 mg/L.Under this concentration, the filaments could grow rapidly and the filaments of S.lomentaria were dark brown, moreover the sporangial branchlets ratio could achieve(46.78%±0.14%)and the sporangium diameter could increase to(18.78±2.45)μm after being cultured for 20 days.Whereas, the filaments grew slowly and pigment of the filaments of S.lomentaria was light with the addition of NO₃^--N at the concentrations of 0, 96.00 and 192.00 mg/L, the sporangial branchlets ratio were(0%±0%), (9.06%±0.32%)and(7.65%±0.45%), respectively, and the sporangium diameter were only about 9.00-10.00 μm after being cultured for 20 days;(3)The optimal addition concentration of PO₄^3--P for the growth and development of filaments of S.lomentaria was 1.32 mg/L.Under the concentration, the filaments could grow rapidly, moreover, the filaments of S.lomentaria were dark brown, the sporangial branchlets ratio could achieve(47.12%±0.26%), the sporangium diameter was 18.89 μm after being cultured for 20 days.However, the sporangial branchlets ratio was only(18.89±0.98)μm and the sporangium diameter was just(9.78±1.32)μm after being cultured for 20 days with the addition of PO₄^3--P at 0 mg/L, and the filaments of S.lomentaria were turned virescent, the cells were cytoclasis and there was no formation of the sporangial branchlets with the addition of PO₄^3--P exceeding 15.84 mg/L.The results mentioned above revealed that it was good for the filaments of S.lomentaria to grow rapidly, enhance the sporangial branchlets ratio and magnify sporangium diameter based on selecting a suitable culture medium and controlling the concentration of nitrate and phosphate within limits in the stage of growth and development of filaments of S.lomentaria.