Abstract: With the progress of nitrogen injection exploitation in the Tahe Oilfield, the nitrogen content in the produced gas is rising continuously, resulting in the failure to reach the standard of the heat value of natural gas, so it is necessary to conduct the study of the safety and economy of the nitrogen-containing natural gas reinjection. In this paper, the safety of nitrogen-containing gas injection was discussed in three aspects: the corrosion rate of gas injection wells, the explosion limit and the critical O₂ ratio. Furthermore, the energy consumption of nitrogen-containing natural gas reinjection process and that of pressure swing adsorption (PSA) nitrogen injection process were compared. The results showed that O₂ in nitrogen-containing natural gas from Tahe Oilfield has no corrosive risk to gas injection wells. Additionally, the range of nitrogen-containing natural gas explosion limit was narrow under the gas injection pressure, and the O₂ contents in nitrogen-containing natural gas was much lower than its critical O₂ ratio, which means that nitrogen-containing natural gas process has no risk of explosion and can be considered safe. The comparison of the process showed that the energy consumption of nitrogen-containing natural gas reinjection process was only one-third of that of the PSA nitrogen injection process, indicating that nitrogen-containing natural gas reinjection process was more economical.