Abstract: To investigate the influences of reservoir permeability and watered?out severity on indigenous microbial enhanced oil recovery (IMEOR), indigenous pseudomonas aeruginosa WJ?1, a high-yield biosurfactant strain, was injected into the core samples of different values of permeability (37.9~505.5 mD) after primary water flooding in the reservoir condition of District-mid?6 in Karamay oilfield, and then the surface tension (ST) and oil?water interfacial tension (IFT) of produced fluid after secondary water flooding were measured to correlate and analyze the variations of the IMEOR, ST and IFT. In addition, the core samples with same permeability was flooded by primary water injection to reach the water cuts of 5%, 35%, 65% and 98%, which mean non?watered?out, weak watered?out, medium watered?out and heavily watered?out reservoir environments, respectively, with which the WJ?1 biosurfactant was injected into the same core samples to correlate the effect of such a IMEOR. The experimental results show that the effect produced by the IMEOR process distinctly increases with the reservoir permeability increasing. Compared with low?permeability core samples, the high?permeability core sample of 505.5 mD has the best effect by using the IMEOR process, with additional EOR of 5.42%, low ST of 70.0 mN/m reducing from 72.0 mN/m and low IFT of 5.9 mN/m reducing from 12.0 mN/m. Also, the effect by IMEOR process reduces with the increasing of reservoir watered?out severity. Injecting the WJ?1 biosurfactant into the core samples when the water cut in the produced fluid reaches 5% after primary water flooding,21.98% of additional EOR can be gained