Use optimized indigenous microbial flora biotechnology to conduct repair experimental research on oilc ontaminated groundwater in loess area of north Shaanxi. The selected optimized flora include Pseudomonas¡¢Micrococcus¡¢Actinomayces¡¢Penicillium¡¢Aspergillus £»During experiment process, add 1.5%¡¯s optimized flora preparation into the polluted waters with oil content of 182.0mg / 862.5mg / l and1695.0mg / l. After some days¡¯ remediation experiments, the maximum cumulative removal rates of oil pollutants in the three concentrations are 53.46% (28d), 70.87% (37d) and58.19% (37d); temperature is one of the remediation affecting factors and 30¡æ is the best flora growth temperature, with the most significant remediation effect on oil-contaminated groundwater, concentration is another important factor influencing oil pollutants, in sterile contrast experiment, the removal rate of oil pollutants is within 5%, indicating slow groundwater oil degradation speed in natural conditions.