Abstract:Due to the special living environment， marine microalgae can synthesize high value -added metabolites and become an important way of natural antibiotics screening. In this study， the antimicrobial activities of different solvent extracts and the fractions against four kinds of pathogenic bacterias were detected with filter paper method. And the crude extracts from petroleum ether phase （PE） were separated and purified by methods of column chromatography and thin layer chromatography （TLC）. The results showed that six kinds of extracts all presented strong inhibitionl effect on Escherichia coli under higher test concentration. Besides， the extracts from Ethanol phase showed high inhibition activities on the other three test bacterials， but the crude extract from PE only had certain antimicrobial activities against Pseudomonas aeruginosa. The extracts from ethyl acetate （EA） and n-butyl alcohol （BA） showed obvious inhibition effect on Monilia albican. The crude extract of PE was further separated to abtain three high purity components， and the complexity analysis results showed that PE Ⅲ-5-1 was chlorophyll compounds， PEⅤ-1 included was the highest ketones， accounting for 55.74 %， followed by ester， and PEⅤ-2 was the most esters， accounting for 50.54 %， followed by ketones and organic acids.