A quantitative research was maken on the Antarctic diatoms,which is very important part of the Antarctic phytoplankton,to find the quantity and characteristics of community structure of planktonic diatom. 6 sample sities were set in the Great Wall Bay,Antarctica and 3 samples of planktonic diatom were collected in each sampling point. 31 kinds of planktonic diatom were found in the area. The dominant species of planktonic diatom communities are Cocconesi fasciolate( 18. 5%),Amphora holsatica( 13. 6%). The s...