The male and female gametophytes of Saccharina japonica ‘Dongfang No.7’ were cultured at different temperatures, photoperiods and nitrogen concentrations to observe the development of gametophytes and explore the optimum environmental conditions for the formation of gametophyte oogonium, ovulation and young sporophyte. The results showed that temperature, photoperiod and nitrogen concentration had significant effects on the development of gametophyte. The rate of gametophyte development at 12 ℃ and 15 ℃ (60%-70%) was significantly higher than that at other temperature groups. At 20 ℃, the gametophyte was in the vegetative growth stage without development. The rate of gametophyte development (80%) in 10L∶14D group was significantly higher than that in other photoperiod groups, followed by that in 6L∶18D group, but the length of young sporophyte in this condition was significantly lower than that in other photoperiod groups. When the concentration of N was 2 mg/L and 4 mg/L, the final development rate was more than 75%, and the sporophyte accounted for about 70%, which was significantly higher than other groups. This study provides theoretical basis and data support for artificial breeding of gametophyte of S.japonica ‘Dongfang No.7’.