Oilfield produced water has a high concentration of pollutants and lacks elements such as N and P needed for biological growth. Domestic sewage is rich in N and P，but the discharge fluctuates greatly，and the cost of separate treatment is high. In order to improve the biological treatment efficiency and reduce the treatment cost of oilfield sewage，the simulated oilfield produced water was mixed with the simulated domestic sewage for microalgae-bacteria symbiosis culture，and then the effects of different volume mixing ratios of produced water and domestic sewage（1∶3，1∶5，1∶15，1∶35）on the growth of organisms and the removal of nutrients were investigated. The microalgae was Chlorella vulgaris，while the strains were composed of Saccharomyces cerevisiae，Lactobacillus，Nitrobacter and Bacillus subtilis. The results showed that the biomass，algal density，bacterial density and chlorophyll of different ratios of produced water/domestic sewage mixtures basically presented an increasing trend with the increase of incubation time. Microalgae-bacteria grew best in the produced water/domestic sewage mixture with a mixing ratio of 1∶3. The total biomass was 0.55 g/L after 7 d of incubation，of which the algal density was 0.23 g/L and the bacterial density was 0.32 g/L. The high ratio of produced water/domestic sewage mixture was favorable for the growth of algae. The highest content of algal chlorophyll a was 649.27 μg/mg after 7 d of incubation in the produced water/domestic sewage mixing ratio of 1∶3，while the highest content of algal chlorophyll b was 821.23 μg/mg in the mixing ratio of 1∶5. In the aspect of nutrient removal，the sewage with a high mixing ratio was more favorable for the nutrient absorption by microalgae-bacteria. The highest removal rates of organic matter and ammonia-nitrogen were obtained when the mixing ratio of produced water and domestic sewage was 1∶3. Meanwhile， the removal rate of chemical oxygen demand（COD）was 65%，and that of ammonia-nitrogen was 37%. The water sample with a mixing ratio of produced water and domestic sewage of 1∶5 had the best removal of total phosphorus，with a removal rate of 70%. Mixing oilfield produced water and domestic sewage in appropriate volume ratio could promote the growth of algae-bacteria and improve the efficiency of biological treatment.