In order to reveal the relationship between the changes of biochemical indexes in produced fluid and the effect of increasing production in oil well，indigenous microbial flooding field test was carried out in four injection wells and 11 production wells of Keshang conglomerate reservoir in mid-7 district of Karamay oilfield. Biochemical index of the test wells，including total viable count in produced fluid，hydrocarbon-oxidizing bacteria（HOB）number，sulfate-reducing bacteria（SRB）number，nutrients （total sugar and total nitrogen），acetate ion concentration，water quality and aqueous phase surface tension，etc，were tracked and monitored. The results of test showed that indigenous microbes could increase the total number of bacteria with 1—2 orders of magnitude and the number of HOB with 2 orders of magnitude. The SRB was inhibited. The higher the number of live bacteria and HOB，the more obvious effect was. The average concentration of acetate ion per well increased to 8.0 mg/L after microbial flooding measures. The total sugar and total nitrogen content were less than 10% of that with injected nutrient，and the change of monitoring period was not obvious. It would be a higher utilization rate on the condition of activator nutrients injected into the reservoir. While the change of aqueous phase surface tension，water salinity and pH value was little，which had little impact on the effect of increasing production.