ABSTRACT:In this study, the microbial community and the physico-chemical properties of soil samples from seven oil-fields in the north of China were analyzed using multiple methods. The study's purpose was to analyze the influence of abiotic factors on the microbial activity and the biotic community. By using the Ultrasonic-Soxhle extraction method of hydrocarbon in oil composition were analyzed, and column chromatography combined with GC-MS was used to analyze the contaminant composition. The results showed that the highest oil concentrations in the soil reached 97.3 g/kg dry soil, which amounts to about 500-1,000 times higher than the background in uncontaminated soil. Moreover, the average nutrient content of contaminated soils was lower than the unpolluted controls. The total bacterial load in the soil was measured using the most probable number (MPN) method and the microbial activity was determined by fluorescein diacetate (FDA) activity. The results showed that soil contaminated with oil seriously affects and limits the microbial populations and their activities. The water content of the soil was the key limiting factor of the microbial populations and the FDA activity. With a water content of 6%, oil content below 15%, and a pH of 7.5-8.0, the conditions supported the highest levels of microbial growth and activity. Microbial populations were 10-100 times and the FDA activity was 2-5 times lower in samples originating from the arid Northwest of China compared to samples from Northwest China. In the northwestern region the microbial diversity was 3 times higher. The microbial communities were limited and suppressed whereby the local environment, the temperature, the water content and the oil content were the key factors that induced the biodiversity of the soil contaminated with oil in different analyses of the geography and the climate environment.