Two strains of bacteria degrading polycyclic aromatic hydrocarbons (PAHs) were isolated using enrichment cultures of various heavy crude oil samples obtained from the Dagang Oilfield. The strains, namely S17 and S28, are able to degrade crude oil using phenanthrene as the sole carbon and energy source. The crude oil composition analysis indicates both strains are able to degrade heavy hydrocarbon components in crude oil. Then, the viscosities of heavy crude oil with S17 and S28 were decreased, and the surface tension between fermentative fluid and air were also decreased. The core flooding tests demonstrated that the fermentation broth, containing the two strains, can improve the residual oil recovery ratio by approximately 12.26% after polymer flooding.