are bioresources important for a wide range of applications in aquaculture, environmental treatment, medicine, agriculture and industry. For instance, Skeletonema costatum have served as natural feed of aquatic animals; have been widely used to their high content of carotenoids. Although more than 0.2 million species exist on earth, only a very small proportion of microalgae have been exploited. In China, approximately 600 microalgal species have been identified, of them less than 10 species have been cultured on large-scales so far. Isolation and identification of more strains from natural environments is thus foundamental and always appreciated by researching and exploiting communities. Yellow Sea and Bohai Sea are rich in phytoplankton and deemed to be an important microalgal repository. However, the reports on the isolation and cultivation of microalgae inhabiting these sea areas are very scarce. In order to promote the exploitation of microalgal resource in Yellow Sea and Bohai Sea, a surveying cruise was carried out in summer 2011, during which the diversity of net collected microalgae was determined. Moreover, a rich collection of cultivable microalgal strains were successfully isolated from 71 stations. A total of 44 species in 30 genera, 4 phyla, were identified in fixed summer seawaters. Among them, Bacillariophytas (28 species in 20 genera) accounted for 51.8%; while dinophytas (14 species in 8 genera) accounted for 23.2%. One speceis in phylum Chrysophyta (Coscinodiscus sp. and which appeared in almost all stations were dominant species. In total, 92 microalgal strains were isolated and purified with diverse methods including capillary catching, streak plating and serial diluting, alone or in combination. Molecular systematic analysis identified the isolated as 19 species including 9 bacillariophytas, 3 phaeophytas, 3 heterokontaes, 2 chlorophytas, 1 dinophytas and 1 haptophyte. The isolated species were mainly small in size, of them 9 in chlorophyta, phaeophyta, heterokonatae and haptophyte were in pico-size, and 10 in bacillariophyta and dinophyta were in nano-size. Among all isolated strains, those in genera Nannochloropsis were expected to be important for EPA production due to their high EPA content; 7 chlorophytas may serve as the candidates for biodiesel production; and 8 Bicosoecales in heterokontae promised for high biomass production therough fermentation and further environmental pollution bioremediation. In spite of the abundance of microalgae in Yellow Sea and Bohai Sea, almost all species we fixed and identified by morphology were difficult to cultivate. sp. (in nano-size) were the only two species observed in fixed seawater and survived laboratory culture. Although the algae in micro-size, , accounted for a large portion in fixed samples, they were unable to survive laboratory culture. Technical means need further optimization in order to get as many cultivable microalgae as possible. We found that distribution of cultivable microalgae is wide in seawaters. Bacillariophytas spread the whole area, and centralized in Laizhou Bay; while the harmful nutriments rich thus facing the risk of red tide. Chlorophytas and haptophyte were mainly collected from north Yellow Sea, a few chlorophytas also collected around Port of Tongxhan. Most phaeophytas were collected from the coasts of and Liaodong Peninsula. Most heterokontaes were collected from north Yellow Sea. In additon, it was the first report that inhabits Chinese coastal seawater.