Daqing oilfield; oil-contaminated soil; alkaline soil; multi-plant system; phytoremediation Abstract: Daqing oil-contaminated alkaline soil and high concentrations oil-pollutant samples were mixed at the ratio of 4:1, 2:1, 1:1 and 1:2 (vsoil/voil), respectively. Then the oil content of the mixed samples were detected and analyzed after phytoremediation experiment with multi-plant systems. The research results showed that Salsola collina Pall-Chinese wildrye-Thistle Herb-Medicago-Artemisia ordosica multi-plant system had a good degradation effect on oily-pollutants. During the 105-day experiment, the degradation rate of oil-pollutants could be up to 80.5% in the mixed soil (4:1, vsoil/voil). During the whole experiment, removal rate of total petroleum hydrocarbons (TPHs) could raise up 65.5% in the Coronilla varia-Lolium perenne-Amaranthus hypochondriacus multi-plant system mixed soil (2:1, vsoil/voil). Experimental results proved that the degradation effect on TPHs could be improved by the multi-plant systems and they could be reasonably matched to cure and restore the ecological environment of oil-contaminated soils.