Based on the observation and comparative analysis, overall and systematic development of M．latissimum in the stages from conjugation of gamete to discharge of zoospore, on the sporophyte stage during the life history of M．latissimum is entirely expatiated in this article. Meanwhile, on the basis of the results of the experiment, we divided the sporophyte stage of M．latissimum into five periods : conjugation of gametes（gamete 7.5 μm×2.0 μm）, zygocyte （4-20 μm）, sporange （18-40 μm）, zoospore formation （sporange 35-55 μm） and discharge of zoospore （zoospore 9.4 μm×3 μm）. In this paper it may be in China to find the systemic acknowledgement on the division of the sporange stage during the life history of Monostroma as well as to the seedling cultivation in practice. 