Marine microorganisms, which are taxonomically diverse and genetically special, have powerful potential in producing novel bio-active substances. This article summarized research progress in this respect. The results showed that marine bacteria which are main marine microorganism flora can produce rich kinds of bio-active substances and that even though marine actinomycetes and marine fungi are not as many as marine bacteria in species and quantity, they should be paid no less attention about their bio-active substances. Besides, present research are limited to those marine microorganisms which are easily cultured. One of the future research trends will be focused on bio-active substances derived from non-culturable marine microorganisms.