Abstract: Embodiments of the invention relate to a mixed bacteria producing surfactant and its screening method. According to at least one embodiment, there is provided a mixed bacteria producing biosurfactant composed of three kinds of strains: Pseudomonas stutzeri with preservation No. CCTCC AB 205091, Nocardioides ginsengagri with preservation No. CCTCC S2013441, and Bacillus licheniformis with preservation No. CCTCC AB 205141. The mixed bacteria is obtained by choosing the bacterial strain for oil production awaiting screening, activating and culturing it, getting the fermentation liquid in primary screen with blood plate method, and re-screening fermentation liquid in primary screen with oil drain method. This mixed bacteria synthesizes the advantages of the three strain, thus producing a biosurfactant to enhance oil recovery in the oilfield.