In this research,by using experimental ecology to imitate the culture conditions of sporelings of Scytosiphon lomentaria,the filaments of S.lomentaria and the natural sand filtered seawater were used as the experimental material and the culture solution,respectively.Different light intensity which includes 7.2,18.0,27.0,36.0,45.0,54.0,72.0,127.0 μmol/(m²·s)were set to study the effect of light intensity 7.2-126.0 μmol/(m²·s)on spore germination,early development of sporelings of S.lomentaria and the dynamic change of epiphytic algae.The results indicated that:(1)27.0-72.0 μmol/(m²·s)was the appropriate light intensity range for the spore germination of S.lomentaria,and the spore germination rate reached the maximum under the condition of 45.0 μmol/(m²·s),the germination rate was 44.44% after 16 days of the spores releasing.(2)In the natural sand filtered seawater,36.0-54.0 μmol/(m²·s)was the appropriate light intensity range for the early development of sporelings,and the optimal light intensity was 45.0 μmol/(m²·s),under whose condition the epiphytic algae density was the lowest and the epiphytic algae density was 38.4×10⁴ ind/cm² after 34 days of the spores releasing.(3)In this study,a total of 29 taxa which belong to 13 genera of 2 phyla were identified,and the main dominant species were Nitzschia frustulum,Pseudo-Nitzschia sicula,Oscillatoria laetevirens,Chroococcus turgidus,Auricula sp. and Nitzschia closterium.Nitzschia frustulum showed exponential growth trend under the condition of 7.2-18 μmol/(m²·s),while Auricula sp. and N.closterium presented exponential growth trend under the condition of 27.0-126.0 μmol/(m²·s).In conclusion,45.0 μmol/(m²·s)was the optimal light intensity for spore germination and early development of sporelings of S.lomentaria.The epiphytic algae,which should be controlled in the process of sporelings production,were Auricula sp. and N.closterium.