Abstract: The commercial 0^# diesel was used as the only source of carbon to screen out bacteria for diesel biodegradation and two strains were identified, i.e., Y1 Bacillus and Y2 Flavobacterium. Both were selected according to their morphological, physiological and biochemical characters. Then, their growing curves were plotted through tests to offer certain evidences for the immobilization of microorganism species and further study on the characters of biodegradation of the two bacteria strains in diesel. The results showed that when the initial oil concentration is 150 mg/L, and the strain Y1 or Y2 after batch culturing for 48 h has been inoculated into the diesel in a ratio of 1/10, the oil removal rate of Y1 and Y2 is 79.5% and 77.23%, respectively, and the effects of oil biodegradation of both Y1 and Y2 decrease with increasing initial oil concentration. It was also observed that the pH value affects greatly the physiological characteristics of Y1 and Y2.