In this paper, the artificial breeding technology of Ulva prolifera on a large scale was studied.Firstly, the effects of temperature and thallus density on the releasing of spores from blades of U.prolifera, and effects of temperature and light intensity on attaching and germination of spores from U.prolifera blades were studied.The results indicated that the quantity of spores releasing from blades of U.prolifera reached the highest when temperature was at 25℃and thallus density was 0.8 g/L; the optimum temperature and light intensity for attaching and germinating of spores released from blades of U.prolifera were 20℃ and sunny days[light intensity>300 μmol/(m²·s)]; and when seedling length reached up to 1-3 cm, it was good for seedlings on nets moving and cultivateing at coast.From Dec 10, 2013 to Jan 26, 2014, the artificial breeding experiment in U.prolifera on a large scale was carried out in Yizhen Seaweed Technology Co., Ltd., Hebosuo Village, Xiangshan Harbor, Fenghua County, Zhejiang Province, China.Basing on the key parameters of artificial breeding, and the technology of artificial breeding in U.prolifera on a large scale was initially established.About 17.82×10¹⁰ spores were released from 6.6 kg fresh thallus, and the average spores releasing rate was about 2.7×10⁷ spores/g.Totle about 2 000 nets (16 m length×1.0 m width) were used for breeding, and average spores attaching rate was about 8.64×10⁷ spores/net.After breeding for 7 days, the germinating rate of spores attaching on nets reached the peak, and the average seedlings density on rope was about 20 seedlings/cm, and the longest of seedlings was about 3 cm.Those parameters met the requests for seedlings cultivating at coast.Whole breeding took 45 days.It would lay a foundation for establishing the artificial breeding technology of U.prolifera on a large scale.