A halophilic bacterial strain TM-1 was isolated from the reservoir of the Shengli oil field in East China. Strain TM-1, which was found to be able to degrade crude oils, is a gram-positive non-motile bacterium with a coccus shape that can grow at temperatures of up to 58 ℃ and in 18% NaCl solution. Depending on the culture conditions, the organism may occur in tetrads. In addition, strain TM-1 pro-duced acid from glucose without gas formation and was catalase-negative. Furthermore, strain TM-I was found to be a facultative aer-obe capable of growth under anaerobic conditions. Moreover, it produced butylated hydroxytoluene, 1,2-benzenedicarboxylic acid-bis ester and dibutyl phthalate and could use different organic substrates. Laboratory studies indicated that strain TM-1 affected different heavy oils by degrading various components and by changing the chemical properties of the oils. In addition, growth of the bacterium in heavy oils resulted in the loss of aromatic hydrocarbons, resins and asphaltenes, and enrichment with light hydrocarbons and an overall redistribution of these hydrocarbons.