Abstract: We studied the characteristics of phytoplankton community in mesh enclosure isolated pond with polyculture of Litopenaeus vannamei and Mugil cephalus. Shrimp ponds were stocked with M.cephalus inside the mesh enclosure at densities of 0 (M0), 250 (M250), 500 (M500) and 800 (M800), respectively. Totally 7 phylums, 39 genera and 65 species of phytoplankton were identified, among which Chlorphyta (21 genera and 33 species) was the most abundance phylum, followed by Cyanophyta (7 genera and 17 species). The pond was dominated by Chlorella vulgaris (up to 50%). In general, phytoplankton abundance increased with increasing density of M.cephalus. In end stage, M250 attained the lowest abundance of blue-green algae and the highest abundance of green algae, both of which presented significant differences with M0 (P＜0.05). In addition, the diversity index of M250 was the highest among the treatments. Better growth of algae was observed in M500 and M800 (with higher mullet stocking densities) in early and middle stages, and in group M500 (with lower mullet stocking density) in late stage. The results indicate that mesh enclosure isolated pond with polyculture of L.vannamei and M.cephalus could achieve higher density of green algae, lower blue-green algae and higher diversity of phytoplankton community.