Abstract: The composition and quantity variation of Heterotrophic bacteria in slime bio films, formed in the marine water on the surfaces of antifouling paint, anticorrosive paint, steel and glass substrates, were investigated in this article. The results indicated that heterotrophic bacteria consist of Aeromonas, Photobacterium, Pseudomonas, Vibrio, Alcaligenes, Chromobacterium, Moraxella etc, and that Aeromonas is the pioneering genus and predominant group in primary stage, but in the whole procedure of experiment the predominant group varies successively and frequently and the vary trend of bacterial quantity on the four substrates is almost the same. The quantity of bacteria on antifouling and anticorrosive paint substrates are higher than that on the surface of steel and glass substrates, and the bacterial species are less. Bacterial quantity on the surface of antifouling paint is the highest in these four substrates, reaching 10⁷cfu/cm².