The Chinese government is seeking CO2 gas emission reduction measures. CO2 capture and geological sequestration is one of the main measures. Injecting CO2 into oil reservoirs can not only achieve the environmental protection purpose of CO2 geological sequestration but also improve oil recovery and realize economic benefits, which helps to offset the cost of CO2 sequestration. Therefore, the oil reservoir is one of the best sites for CO2 sequestration. As for the reservoir of CO2 flooding after water flooding, there are two methods for evaluating the potential of CO2 enhanced oil recovery (EOR) and sequestration capacity, which are the mass balance method and analogy method. Through a combination of these two methods, this paper presents a new method, which can be reasonably used to evaluate these potentials. Besides, the screening criteria of CO2 sequestration and EOR in the Junggar Basin are also proposed. On the basis of the guidelines of CO2 source matching, reservoir characteristics, and fluid characteristic, four typical low permeability reservoirs (Caiman oil reservoir, Kararnay oil reservoir, Beisantai oil reservoir, and Luliang oil reservoir) of the Junggar Basin are selected to study their potential of CO2 EOR and sequestration. And then the potential of CO2 EOR and sequestration capacity for the Junggar Basin oil reservoirs of CO2 flooding after water flooding is studied by applying the method mentioned above. For 275 development blocks of 24 oil fields in the Junggar Basin, 139 development blocks are suitable for CO2 miscible flooding EOR and sequestration, whereas 136 development blocks are suitable for CO2 immiscible flooding EOR and sequestration. The total EOR potential could be 18 407.76 X 10(4) t and the CO2 sequestration potential could amount to 47486.0 x 10(4) t. The evaluation results show that the Junggar Basin's oil reservoirs are suitable sites for CO2 EOR and sequestration and have great potentials. It can provide the decision basis for the future implementation of CO2 emission reduction projects in Western China.