The invention relates to a method and a device for sampling a produced fluid of an oil reservoir for microbial flooding. The technical scheme comprises the following steps of: (1) test and control of the temperature and pressure of the oil reservoir; (2) anaerobic treatment for the sampling device; (3) high-temperature and high-pressure separation of oil, gas and water; (4) anaerobic and high-pressure sampling of the oil, the gas and the water; (5) on-line test of oil, gas and water samples; and (6) processing and remote transmission of oil, gas and water test results. The invention has the advantages of solving the problem of the sampling of oil, gas and water mixtures under high-temperature, high-voltage and anaerobic conditions, ensuring that materials cannot diffuse on the spot during the sampling so as to protect on-site environment, ensuring that recovered crude oil and gas can be effectively utilized, ensuring the accuracy and reliability of parameter testing of the produced fluid of the oil reservoir of the microbial flooding, improving the accuracy of microbial community structures by over 30 percent and the accuracy of oxidation-reduction potential by over 40 percent, and providing a reliable theoretical basis for the ecological regulation and control of the oil reservoir of the microbial blooding.