Abstract: For clarifying the development and ecological adaptability of juvenile sporophytes of Macrocystis pyrifera,the effects of photoperiod(10 L:14 D,12 L:12 D,14 L:10 D,16 L:8 D)on gametophyte clone seed-rearing of M.pyrifera were studied.And,the impacts of light intensity,temperature,nutrients concentration on the growth,net photosynthetic rate(P_n),dark respiratory rate(R_d)of sporophytes(0.5-1 cm)of Macrocystis pyrifera were investigated by single factor test and orthogonal experiment.The major results included:(1)Large numbers of gametophytes developed into sporophytes at long photoperiod(14 L:10 D,16 L:8 D).(2)The highest value for relative growth rate(RGR)and P_n were observed at 70 μmol/(m²·s)light intensity,13℃ temperature and 2 mg/L nitrogen concentration(N:P=10:1,the same below).The growth of sporophytes was inhibited when exposure to 90 μmol/(m²·s),RGR of which was significantly lower than other tests.RGR at 10℃ was significantly lower than that at 13℃(P<0.05).And RGR significantly decreased when exposure to 8 mg/L nitrogen concentration.(3)P_n and R_d presented the rising trend with increased nutrients concentration.P_n of 0.2 mg/L group was significantly lower than that at 6 mg/L and 8 mg/L group.R_d significantly different compared with other groups while cultured at 0.2 mg/L(P<0.05).(4)P_n decreased with rising of temperature while cultured at the same light intensity.At the range of 40-80 μmol/(m²·s),P_n was significantly different between 10,13 group and 16,19℃ group.According to orthogonal experiment,the optimum light intensity,temperature and nitrogen concentration for cultivation of sporophytes of M.pyrifera were 40-70 μmol/(m²·s),13℃ and 2 mg/L.Our results provide guidance for the optimization of artificial breeding technologies for M.pyrifera.